diff --git a/.github/workflows/js_interop.yaml b/.github/workflows/js_interop.yaml
index 2ea53e8c..4269e4eb 100644
--- a/.github/workflows/js_interop.yaml
+++ b/.github/workflows/js_interop.yaml
@@ -25,7 +25,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        sdk: ['3.10', beta, dev]
+        # Add back in 3.12 when it's stable
+        sdk: [beta, dev]
         test_config: ['-p chrome', '-p chrome -c dart2wasm', '-p node']
 
     steps:
diff --git a/.github/workflows/js_interop_gen.yaml b/.github/workflows/js_interop_gen.yaml
index 1d486215..4f218ca1 100644
--- a/.github/workflows/js_interop_gen.yaml
+++ b/.github/workflows/js_interop_gen.yaml
@@ -25,7 +25,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        sdk: ['3.10', dev]
+        # Add back in 3.12 when it's stable
+        sdk: [beta, dev]
         test_config: ['', '-p chrome', '-p chrome -c dart2wasm']
 
     steps:
diff --git a/.github/workflows/web.yaml b/.github/workflows/web.yaml
index e10b6933..45d85655 100644
--- a/.github/workflows/web.yaml
+++ b/.github/workflows/web.yaml
@@ -25,8 +25,9 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        sdk: ['3.10', beta, dev]
-        test_config: ['-p chrome', '-p chrome -c dart2wasm']
+        # Add back in 3.12 when it's stable
+        sdk: [beta, dev]
+        test_config: ['-p chrome -c dart2js', '-p chrome -c dart2wasm', '-p vm']
 
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
diff --git a/.github/workflows/web_generator.yaml b/.github/workflows/web_generator.yaml
index f136b8af..53e7eade 100644
--- a/.github/workflows/web_generator.yaml
+++ b/.github/workflows/web_generator.yaml
@@ -27,7 +27,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        sdk: ['3.10', dev]
+        # Add back in 3.12 when it's stable
+        sdk: [beta, dev]
 
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
@@ -51,6 +52,9 @@ jobs:
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
       - uses: dart-lang/setup-dart@65eb853c7ba17dde3be364c3d2858773e7144260
+        with:
+          # Drop this when 3.12 is stable
+          sdk: dev
 
       - run: npm install
       - run: dart pub get
@@ -66,6 +70,9 @@ jobs:
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
       - uses: dart-lang/setup-dart@65eb853c7ba17dde3be364c3d2858773e7144260
+        with:
+          # Drop this when 3.12 is stable
+          sdk: dev
 
       - run: npm install
       - run: dart pub get
diff --git a/js_interop/pubspec.yaml b/js_interop/pubspec.yaml
index c6f23c8f..4dbfd866 100644
--- a/js_interop/pubspec.yaml
+++ b/js_interop/pubspec.yaml
@@ -4,7 +4,7 @@ description: Utility APIs for dart:js_interop and dart:js_interop_unsafe.
 repository: https://github.com/dart-lang/web
 
 environment:
-  sdk: ^3.10.0
+  sdk: ^3.12.0-0
 
 dev_dependencies:
   test: ^1.26.0
diff --git a/js_interop_gen/lib/src/ast/declarations.dart b/js_interop_gen/lib/src/ast/declarations.dart
index d8fcf3a9..83fa2abb 100644
--- a/js_interop_gen/lib/src/ast/declarations.dart
+++ b/js_interop_gen/lib/src/ast/declarations.dart
@@ -76,8 +76,8 @@ sealed class TypeDeclaration extends NestableDeclaration
     this.constructors = const [],
     this.parent,
     this.documentation,
-    required ID id,
-  }) : _id = id;
+    required this._id,
+  });
 
   /// [useFirstExtendeeAsRepType] is used to assert that the extension type
   /// generated has a representation type of the first member of [extendees]
@@ -644,13 +644,13 @@ class NamespaceDeclaration extends NestableDeclaration
   NamespaceDeclaration({
     required this.name,
     this.exported = true,
-    required ID id,
+    required this._id,
     this.dartName,
     this.topLevelDeclarations = const {},
     this.namespaceDeclarations = const {},
     this.nestableDeclarations = const {},
     this.documentation,
-  }) : _id = id;
+  });
 
   @override
   ExtensionType emit([covariant DeclarationOptions? options]) {
diff --git a/js_interop_gen/lib/src/elements.dart b/js_interop_gen/lib/src/elements.dart
index d30d88b7..d88d9799 100644
--- a/js_interop_gen/lib/src/elements.dart
+++ b/js_interop_gen/lib/src/elements.dart
@@ -306,6 +306,28 @@ class Parameter {
   }
 }
 
+class IterableInfo {
+  final RawType? keyType;
+  final RawType valueType;
+  final bool isAsync;
+
+  IterableInfo({this.keyType, required this.valueType, required this.isAsync});
+}
+
+class MaplikeInfo {
+  final RawType keyType;
+  final RawType valueType;
+  final bool isReadOnly;
+  final bool isFromIterable;
+
+  MaplikeInfo({
+    required this.keyType,
+    required this.valueType,
+    required this.isReadOnly,
+    required this.isFromIterable,
+  });
+}
+
 class PartialInterfacelike {
   final String name;
   final String type;
@@ -316,6 +338,8 @@ class PartialInterfacelike {
   final List<Property> extensionProperties = [];
   final MdnInterface? mdnInterface;
   OverridableConstructor? constructor;
+  IterableInfo? iterableInfo;
+  MaplikeInfo? maplikeInfo;
 
   factory PartialInterfacelike(
     idl.Interfacelike interfacelike,
@@ -475,9 +499,43 @@ class PartialInterfacelike {
           );
           break;
         case 'maplike':
+          final decl = member as idl.MemberDeclaration;
+          final types =
+              ((decl.idlType as JSAny) as JSArray<idl.IDLType>).toDart;
+          if (types.length != 2) {
+            throw Exception('Unexpected number of type arguments for maplike');
+          }
+          maplikeInfo = MaplikeInfo(
+            keyType: _getRawType(types[0]),
+            valueType: _getRawType(types[1]),
+            isReadOnly: decl.readonly,
+            isFromIterable: false,
+          );
+          break;
         case 'setlike':
+          break;
         case 'iterable':
         case 'async_iterable':
+          final decl = member as idl.MemberDeclaration;
+          final types =
+              ((decl.idlType as JSAny) as JSArray<idl.IDLType>).toDart;
+          RawType? keyType;
+          late RawType valueType;
+
+          if (types.length == 1) {
+            valueType = _getRawType(types[0]);
+          } else if (types.length == 2) {
+            keyType = _getRawType(types[0]);
+            valueType = _getRawType(types[1]);
+          } else {
+            throw Exception('Unexpected number of type arguments for iterable');
+          }
+
+          iterableInfo = IterableInfo(
+            keyType: keyType,
+            valueType: valueType,
+            isAsync: decl.async,
+          );
           break;
         default:
           throw Exception('Unrecognized member type $type');
diff --git a/js_interop_gen/lib/src/sdk_version.dart b/js_interop_gen/lib/src/sdk_version.dart
index 8e86616c..e7ecbe8e 100644
--- a/js_interop_gen/lib/src/sdk_version.dart
+++ b/js_interop_gen/lib/src/sdk_version.dart
@@ -11,7 +11,7 @@ import 'package:yaml/yaml.dart';
 ///
 /// For the purposes of code generation and tooling, we treat this as the
 /// language version of the SDK.
-final dartLanguageVersion = Version(3, 10, 0);
+final dartLanguageVersion = Version(3, 12, 0);
 
 /// Derives the language version from an SDK constraint.
 Version deriveLanguageVersion(VersionConstraint constraint) {
diff --git a/js_interop_gen/lib/src/translator.dart b/js_interop_gen/lib/src/translator.dart
index 710ac348..7e163018 100644
--- a/js_interop_gen/lib/src/translator.dart
+++ b/js_interop_gen/lib/src/translator.dart
@@ -138,10 +138,10 @@ class Translator {
     this._elementTagMap, {
     this.packageRoot,
     required bool generateAll,
-    bool generateForWeb = true,
+    this._generateForWeb = true,
     this.loadedRenameMap = const {},
     required String bcdJsonPath,
-  }) : _generateForWeb = generateForWeb {
+  }) {
     instance = this;
     docProvider = DocProvider.create();
     browserCompatData = BrowserCompatData.read(
@@ -817,6 +817,419 @@ class Translator {
     for (final operation in operations) _operation(operation),
   ];
 
+  List<code.Method> _generateMaplikeMethodsOnExtension(
+    String dartClassName,
+    MaplikeInfo info,
+    bool Function(String) hasOperation,
+  ) {
+    final keyInteropType = _typeReference(
+      info.keyType,
+      onlyEmitInteropTypes: true,
+    );
+    final valueInteropType = _typeReference(
+      info.valueType,
+      onlyEmitInteropTypes: true,
+    );
+
+    return [
+      if (!hasOperation('get'))
+        code.Method(
+          (b) => b
+            ..name = 'get'
+            ..annotations.addAll(_jsOverride('', alwaysEmit: true))
+            ..external = true
+            ..returns = valueInteropType.rebuild((b) => b..isNullable = true)
+            ..requiredParameters.add(
+              code.Parameter(
+                (b) => b
+                  ..name = 'key'
+                  ..type = keyInteropType,
+              ),
+            ),
+        ),
+      if (!hasOperation('has'))
+        code.Method(
+          (b) => b
+            ..name = 'has'
+            ..annotations.addAll(_jsOverride('', alwaysEmit: true))
+            ..external = true
+            ..returns = code.refer('bool')
+            ..requiredParameters.add(
+              code.Parameter(
+                (b) => b
+                  ..name = 'key'
+                  ..type = keyInteropType,
+              ),
+            ),
+        ),
+      if (!info.isReadOnly) ...[
+        if (!hasOperation('set'))
+          code.Method(
+            (b) => b
+              ..name = 'set'
+              ..annotations.addAll(_jsOverride('', alwaysEmit: true))
+              ..external = true
+              ..returns = code.refer('void')
+              ..requiredParameters.addAll([
+                code.Parameter(
+                  (b) => b
+                    ..name = 'key'
+                    ..type = keyInteropType,
+                ),
+                code.Parameter(
+                  (b) => b
+                    ..name = 'value'
+                    ..type = valueInteropType,
+                ),
+              ]),
+          ),
+        if (!hasOperation('delete'))
+          code.Method(
+            (b) => b
+              ..name = 'delete'
+              ..annotations.addAll(_jsOverride('', alwaysEmit: true))
+              ..external = true
+              ..returns = code.refer('bool')
+              ..requiredParameters.add(
+                code.Parameter(
+                  (b) => b
+                    ..name = 'key'
+                    ..type = keyInteropType,
+                ),
+              ),
+          ),
+        if (!info.isFromIterable && !hasOperation('clear'))
+          code.Method(
+            (b) => b
+              ..name = 'clear'
+              ..annotations.addAll(_jsOverride('', alwaysEmit: true))
+              ..external = true
+              ..returns = code.refer('void'),
+          ),
+      ],
+      if (!hasOperation('keys'))
+        code.Method(
+          (b) => b
+            ..name = 'keys'
+            ..annotations.addAll(_jsOverride('', alwaysEmit: true))
+            ..external = true
+            ..returns = code.TypeReference(
+              (b) => b
+                ..symbol = 'JSIterator'
+                ..types.add(keyInteropType),
+            ),
+        ),
+      code.Method(
+        (b) => b
+          ..name = 'asMap'
+          ..type = code.MethodType.getter
+          ..returns = code.TypeReference(
+            (b) => b
+              ..symbol = 'Map'
+              ..types.addAll([
+                _typeReference(info.keyType),
+                _typeReference(info.valueType),
+              ]),
+          )
+          ..lambda = true
+          ..body = code.Code('_${dartClassName}MapView(this)'),
+      ),
+    ];
+  }
+
+  code.Class _generateMaplikeViewClass(String dartClassName, MaplikeInfo info) {
+    final className = '_${dartClassName}MapView';
+    final rawKeyType = desugarTypedef(info.keyType) ?? info.keyType;
+    final keyType = _typeReference(info.keyType);
+    final valueType = _typeReference(info.valueType);
+    final keyInteropType = _typeReference(
+      info.keyType,
+      onlyEmitInteropTypes: true,
+    );
+    final valueInteropType = _typeReference(
+      info.valueType,
+      onlyEmitInteropTypes: true,
+    );
+    final jsObjectType = code.TypeReference((b) => b..symbol = dartClassName);
+    final keyCastType = _typeReference(rawKeyType).symbol;
+    final isInteropKeyCast = keyCastType.startsWith('JS');
+
+    final keyConversion = info.isFromIterable
+        ? 'key'
+        : _toJSCall('key', keyInteropType.symbol);
+    final valueConversion = info.isFromIterable
+        ? 'value'
+        : _toJSCall('value', valueInteropType.symbol);
+    var getConversion = info.isFromIterable
+        ? 'value'
+        : _toDartCall('value', valueInteropType.symbol);
+    if (!info.isFromIterable &&
+        valueType.symbol == 'int' &&
+        valueInteropType.symbol == 'JSNumber') {
+      getConversion = '$getConversion.toInt()';
+    }
+    final keyToDartCall = _toDartCall('e', keyInteropType.symbol);
+    final keysBody = keyToDartCall == 'e'
+        ? 'return _jsObject.keys().toDartIterable;'
+        : 'return _jsObject.keys().toDartIterable.map((e) => $keyToDartCall);';
+
+    final keyTypeCheck = isInteropKeyCast
+        ? 'if (key == null || !(key as JSAny).isA<$keyCastType>()) return null;'
+              'final jsKey = key as $keyCastType;'
+        : 'if (key is! $keyCastType) return null;';
+
+    final keyConversionLocal = isInteropKeyCast
+        ? keyConversion.replaceAll('key', 'jsKey')
+        : keyConversion;
+
+    return code.Class(
+      (b) => b
+        ..name = className
+        ..extend = code.TypeReference(
+          (b) => b
+            ..symbol = info.isReadOnly ? 'UnmodifiableMapBase' : 'MapBase'
+            ..url = 'dart:collection'
+            ..types.addAll([keyType, valueType]),
+        )
+        ..fields.add(
+          code.Field(
+            (b) => b
+              ..name = '_jsObject'
+              ..type = jsObjectType
+              ..modifier = code.FieldModifier.final$,
+          ),
+        )
+        ..constructors.add(
+          code.Constructor(
+            (b) => b
+              ..requiredParameters.add(
+                code.Parameter(
+                  (b) => b
+                    ..name = '_jsObject'
+                    ..toThis = true,
+                ),
+              ),
+          ),
+        )
+        ..methods.addAll([
+          code.Method(
+            (b) => b
+              ..name = 'operator []'
+              ..annotations.add(code.refer('override'))
+              ..returns = valueType.rebuild((b) => b..isNullable = true)
+              ..requiredParameters.add(
+                code.Parameter(
+                  (b) => b
+                    ..name = 'key'
+                    ..type = code.refer('Object?'),
+                ),
+              )
+              ..body = code.Code(
+                valueType.symbol == 'JSArray'
+                    ? '''
+$keyTypeCheck
+final value = _jsObject.get($keyConversionLocal);
+if (value == null) return null;
+return _jsObject.getAll($keyConversionLocal);
+'''
+                    : '''
+$keyTypeCheck
+final value = _jsObject.get($keyConversionLocal);
+if (value == null) return null;
+return $getConversion;
+''',
+              ),
+          ),
+          if (!info.isReadOnly) ...[
+            code.Method(
+              (b) => b
+                ..name = 'operator []='
+                ..annotations.add(code.refer('override'))
+                ..returns = code.refer('void')
+                ..requiredParameters.addAll([
+                  code.Parameter(
+                    (b) => b
+                      ..name = 'key'
+                      ..type = keyType,
+                  ),
+                  code.Parameter(
+                    (b) => b
+                      ..name = 'value'
+                      ..type = valueType,
+                  ),
+                ])
+                ..body = code.Code(
+                  '_jsObject.set($keyConversion, $valueConversion);',
+                ),
+            ),
+            code.Method(
+              (b) => b
+                ..name = 'clear'
+                ..annotations.add(code.refer('override'))
+                ..returns = code.refer('void')
+                ..body = info.isFromIterable
+                    ? code.Code('''
+final keys = _jsObject.keys().toDartIterable.toList();
+for (final k in keys) {
+  _jsObject.delete(${_toDartCall('k', keyInteropType.symbol)});
+}
+''')
+                    : const code.Code('_jsObject.clear();'),
+            ),
+          ],
+          code.Method(
+            (b) => b
+              ..name = 'keys'
+              ..type = code.MethodType.getter
+              ..annotations.add(code.refer('override'))
+              ..returns = code.TypeReference(
+                (b) => b
+                  ..symbol = 'Iterable'
+                  ..types.add(keyType),
+              )
+              ..body = code.Code(keysBody),
+          ),
+          if (!info.isReadOnly)
+            code.Method(
+              (b) => b
+                ..name = 'remove'
+                ..annotations.add(code.refer('override'))
+                ..returns = valueType.rebuild((b) => b..isNullable = true)
+                ..requiredParameters.add(
+                  code.Parameter(
+                    (b) => b
+                      ..name = 'key'
+                      ..type = code.refer('Object?'),
+                  ),
+                )
+                ..body = code.Code(
+                  valueType.symbol == 'JSArray'
+                      ? '''
+$keyTypeCheck
+final values = _jsObject.getAll($keyConversionLocal);
+// ignore: prefer_is_empty
+if (values.length == 0) return null;
+_jsObject.delete($keyConversionLocal);
+return values;
+'''
+                      : '''
+$keyTypeCheck
+final value = _jsObject.get($keyConversionLocal);
+_jsObject.delete($keyConversionLocal);
+if (value == null) return null;
+return $getConversion;
+''',
+                ),
+            ),
+        ]),
+    );
+  }
+
+  code.Method _generateToDartGetter(IterableInfo info) {
+    final isKeyValue = info.keyType != null;
+
+    if (isKeyValue) {
+      final keyInteropType = _typeReference(
+        info.keyType!,
+        onlyEmitInteropTypes: true,
+      );
+      final valueInteropType = _typeReference(
+        info.valueType,
+        onlyEmitInteropTypes: true,
+      );
+
+      final keyDartSymbol = _dartTypeSymbol(keyInteropType.symbol);
+      final valueDartSymbol = _dartTypeSymbol(valueInteropType.symbol);
+
+      final rawKeyType = desugarTypedef(info.keyType!) ?? info.keyType!;
+      final rawValueType = desugarTypedef(info.valueType) ?? info.valueType;
+
+      final keyConversion = _toDartCall(
+        rawKeyType.type == 'JSAny'
+            ? 'e.toDart[0]'
+            : '(e.toDart[0] as ${keyInteropType.symbol})',
+        keyInteropType.symbol,
+      );
+      final valueConversion = _toDartCall(
+        rawValueType.type == 'JSAny'
+            ? 'e.toDart[1]'
+            : '(e.toDart[1] as ${valueInteropType.symbol})',
+        valueInteropType.symbol,
+      );
+
+      return code.Method(
+        (b) => b
+          ..name = 'toDart'
+          ..type = code.MethodType.getter
+          ..lambda = true
+          ..returns = code.TypeReference(
+            (b) => b
+              ..symbol = 'Iterable'
+              ..types.add(
+                code.TypeReference(
+                  (b) => b
+                    ..symbol = '({$keyDartSymbol key, $valueDartSymbol value})',
+                ),
+              ),
+          )
+          ..body = code.Code('''
+toDartIterable.map((e) => (
+      key: $keyConversion,
+      value: $valueConversion,
+    ))'''),
+      );
+    } else {
+      final valueInteropType = _typeReference(
+        info.valueType,
+        onlyEmitInteropTypes: true,
+      );
+      final valueDartSymbol = _dartTypeSymbol(valueInteropType.symbol);
+
+      final body = valueInteropType.symbol != valueDartSymbol
+          ? 'toDartIterable'
+                '.map((e) => ${_toDartCall('e', valueInteropType.symbol)})'
+          : 'toDartIterable';
+
+      return code.Method(
+        (b) => b
+          ..name = 'toDart'
+          ..type = code.MethodType.getter
+          ..lambda = true
+          ..returns = code.TypeReference(
+            (b) => b
+              ..symbol = 'Iterable'
+              ..types.add(
+                code.TypeReference((b) => b..symbol = valueDartSymbol),
+              ),
+          )
+          ..body = code.Code(body),
+      );
+    }
+  }
+
+  String _toJSCall(String sourceExpr, String interopSymbol) =>
+      switch (interopSymbol) {
+        'JSNumber' => '$sourceExpr.toJS',
+        'JSString' => '$sourceExpr.toJS',
+        'JSBoolean' => '$sourceExpr.toJS',
+        _ => sourceExpr,
+      };
+
+  String _toDartCall(String sourceExpr, String interopSymbol) =>
+      switch (interopSymbol) {
+        'JSNumber' => '$sourceExpr.toDartDouble',
+        'JSString' => '$sourceExpr.toDart',
+        'JSBoolean' => '$sourceExpr.toDart',
+        _ => sourceExpr,
+      };
+
+  String _dartTypeSymbol(String interopSymbol) => switch (interopSymbol) {
+    'JSNumber' => 'double',
+    'JSString' => 'String',
+    'JSBoolean' => 'bool',
+    _ => interopSymbol,
+  };
+
   List<code.Method> _cssStyleDeclarationProperties() {
     return [
       for (final style in _cssStyleDeclarations)
@@ -915,11 +1328,26 @@ class Translator {
     required List<OverridableOperation> staticOperations,
     required List<Property> properties,
     required bool isObjectLiteral,
+    IterableInfo? iterableInfo,
+    MaplikeInfo? maplikeInfo,
   }) {
     final docs = mdnInterface == null ? <String>[] : mdnInterface.formattedDocs;
 
     final jsObject = _typeReference(RawType('JSObject', false));
     const representationFieldName = '_';
+    bool hasOperation(String name) {
+      var c = _interfacelikes[jsName];
+      while (c != null) {
+        if (c.operations.containsKey(name)) return true;
+        if (c.inheritance != null) {
+          c = _interfacelikes[c.inheritance!];
+        } else {
+          break;
+        }
+      }
+      return false;
+    }
+
     final legacyNameSpace = extendedAttributes
         .where(
           (extendedAttribute) => extendedAttribute.name == 'LegacyNamespace',
@@ -955,7 +1383,37 @@ class Translator {
         ..implements.addAll(
           implements
               .map((interface) => _typeReference(RawType(interface, false)))
-              .followedBy([jsObject]),
+              .followedBy([jsObject])
+              .followedBy(
+                iterableInfo != null && !iterableInfo.isAsync
+                    ? [
+                        code.TypeReference(
+                          (b) => b
+                            ..symbol = 'JSIterable'
+                            ..url = 'dart:js_interop'
+                            ..types.add(
+                              iterableInfo.keyType != null
+                                  ? code.TypeReference(
+                                      (b) => b
+                                        ..symbol = 'JSArray'
+                                        ..url = 'dart:js_interop'
+                                        ..types.add(
+                                          code.TypeReference(
+                                            (b) => b
+                                              ..symbol = 'JSAny'
+                                              ..url = 'dart:js_interop',
+                                          ),
+                                        ),
+                                    )
+                                  : _typeReference(
+                                      iterableInfo.valueType,
+                                      onlyEmitInteropTypes: true,
+                                    ),
+                            ),
+                        ),
+                      ]
+                    : [],
+              ),
         )
         ..constructors.addAll(
           (isObjectLiteral
@@ -981,6 +1439,20 @@ class Translator {
                 dartClassName == 'CSSStyleDeclaration'
                     ? _cssStyleDeclarationProperties()
                     : [],
+              )
+              .followedBy(
+                iterableInfo != null && !iterableInfo.isAsync
+                    ? [_generateToDartGetter(iterableInfo)]
+                    : [],
+              )
+              .followedBy(
+                maplikeInfo != null
+                    ? _generateMaplikeMethodsOnExtension(
+                        dartClassName,
+                        maplikeInfo,
+                        hasOperation,
+                      )
+                    : [],
               ),
         ),
     );
@@ -1020,6 +1492,50 @@ class Translator {
       _renamedClasses[jsName] = dartClassName;
     }
 
+    var maplikeInfo = interfacelike.maplikeInfo;
+
+    // Lookup iterableInfo from superclasses if not present.
+    var iterableInfo = interfacelike.iterableInfo;
+    var current = interfacelike;
+    while (iterableInfo == null && current.inheritance != null) {
+      final superInterface = _interfacelikes[current.inheritance!];
+      if (superInterface == null) break;
+      iterableInfo = superInterface.iterableInfo;
+      current = superInterface;
+    }
+
+    if (maplikeInfo == null &&
+        iterableInfo != null &&
+        iterableInfo.keyType != null) {
+      bool hasOperation(String name) {
+        var c = interfacelike;
+        while (true) {
+          if (c.operations.containsKey(name)) return true;
+          if (c.inheritance != null) {
+            final superInterface = _interfacelikes[c.inheritance!];
+            if (superInterface == null) break;
+            c = superInterface;
+          } else {
+            break;
+          }
+        }
+        return false;
+      }
+
+      final hasGet = hasOperation('get');
+      final hasSet = hasOperation('set');
+      final hasHas = hasOperation('has');
+
+      if (hasGet && hasHas) {
+        maplikeInfo = MaplikeInfo(
+          keyType: iterableInfo.keyType!,
+          valueType: iterableInfo.valueType,
+          isReadOnly: !hasSet,
+          isFromIterable: true,
+        );
+      }
+    }
+
     return [
       if (getterName != null) _topLevelGetter(rawType, getterName),
       _extensionType(
@@ -1034,7 +1550,11 @@ class Translator {
         staticOperations: staticOperations,
         properties: properties,
         isObjectLiteral: isDictionary,
+        iterableInfo: interfacelike.iterableInfo,
+        maplikeInfo: maplikeInfo,
       ),
+      if (maplikeInfo != null)
+        _generateMaplikeViewClass(dartClassName, maplikeInfo),
       if (extensionProperties.isNotEmpty)
         _extension(type: rawType, extensionProperties: extensionProperties),
     ];
diff --git a/js_interop_gen/pubspec.yaml b/js_interop_gen/pubspec.yaml
index 3863bbc8..e780baf4 100644
--- a/js_interop_gen/pubspec.yaml
+++ b/js_interop_gen/pubspec.yaml
@@ -6,7 +6,7 @@ description: >-
 repository: https://github.com/dart-lang/web
 
 environment:
-  sdk: ^3.10.0
+  sdk: ^3.12.0-0
 
 dependencies:
   analyzer: ^12.0.0
diff --git a/js_interop_gen/test/integration/idl/iterable_expected.dart b/js_interop_gen/test/integration/idl/iterable_expected.dart
new file mode 100644
index 00000000..13dc6529
--- /dev/null
+++ b/js_interop_gen/test/integration/idl/iterable_expected.dart
@@ -0,0 +1,23 @@
+// Generated from Web IDL definitions.
+
+// ignore_for_file: constant_identifier_names, non_constant_identifier_names
+
+@JS()
+library;
+
+import 'dart:js_interop';
+
+extension type ValueIterable._(JSObject _)
+    implements JSObject, JSIterable<JSNumber> {
+  Iterable<double> get toDart => toDartIterable.map((e) => e.toDartDouble);
+}
+extension type KeyValueIterable._(JSObject _)
+    implements JSObject, JSIterable<JSArray<JSAny>> {
+  Iterable<({String key, String value})> get toDart => toDartIterable.map(
+    (e) => (
+      key: (e.toDart[0] as JSString).toDart,
+      value: (e.toDart[1] as JSString).toDart,
+    ),
+  );
+}
+extension type AsyncIterable._(JSObject _) implements JSObject {}
diff --git a/js_interop_gen/test/integration/idl/iterable_input.idl b/js_interop_gen/test/integration/idl/iterable_input.idl
new file mode 100644
index 00000000..d00837fc
--- /dev/null
+++ b/js_interop_gen/test/integration/idl/iterable_input.idl
@@ -0,0 +1,14 @@
+[Exposed=Window]
+interface ValueIterable {
+  iterable<long>;
+};
+
+[Exposed=Window]
+interface KeyValueIterable {
+  iterable<DOMString, DOMString>;
+};
+
+[Exposed=Window]
+interface AsyncIterable {
+  async iterable<long>;
+};
diff --git a/js_interop_gen/test/integration/idl/maplike_expected.dart b/js_interop_gen/test/integration/idl/maplike_expected.dart
new file mode 100644
index 00000000..85bfc300
--- /dev/null
+++ b/js_interop_gen/test/integration/idl/maplike_expected.dart
@@ -0,0 +1,92 @@
+// Generated from Web IDL definitions.
+
+// ignore_for_file: constant_identifier_names, non_constant_identifier_names
+
+@JS()
+library;
+
+import 'dart:collection';
+import 'dart:js_interop';
+
+extension type MyMaplike._(JSObject _) implements JSObject {
+  @JS()
+  external JSString? get(JSString key);
+  @JS()
+  external bool has(JSString key);
+  @JS()
+  external JSIterator<JSString> keys();
+  Map<String, String> get asMap => _MyMaplikeMapView(this);
+}
+
+class _MyMaplikeMapView extends UnmodifiableMapBase<String, String> {
+  _MyMaplikeMapView(this._jsObject);
+
+  final MyMaplike _jsObject;
+
+  @override
+  String? operator [](Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key.toJS);
+    if (value == null) return null;
+    return value.toDart;
+  }
+
+  @override
+  Iterable<String> get keys {
+    return _jsObject.keys().toDartIterable.map((e) => e.toDart);
+  }
+}
+
+extension type MyReadWriteMaplike._(JSObject _) implements JSObject {
+  @JS()
+  external JSString? get(JSString key);
+  @JS()
+  external bool has(JSString key);
+  @JS()
+  external void set(JSString key, JSString value);
+  @JS()
+  external bool delete(JSString key);
+  @JS()
+  external void clear();
+  @JS()
+  external JSIterator<JSString> keys();
+  Map<String, String> get asMap => _MyReadWriteMaplikeMapView(this);
+}
+
+class _MyReadWriteMaplikeMapView extends MapBase<String, String> {
+  _MyReadWriteMaplikeMapView(this._jsObject);
+
+  final MyReadWriteMaplike _jsObject;
+
+  @override
+  String? operator [](Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key.toJS);
+    if (value == null) return null;
+    return value.toDart;
+  }
+
+  @override
+  void operator []=(String key, String value) {
+    _jsObject.set(key.toJS, value.toJS);
+  }
+
+  @override
+  void clear() {
+    _jsObject.clear();
+  }
+
+  @override
+  Iterable<String> get keys {
+    return _jsObject.keys().toDartIterable.map((e) => e.toDart);
+  }
+
+  @override
+  String? remove(Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key.toJS);
+    _jsObject.delete(key.toJS);
+    if (value == null) return null;
+    return value.toDart;
+  }
+}
diff --git a/js_interop_gen/test/integration/idl/maplike_input.idl b/js_interop_gen/test/integration/idl/maplike_input.idl
new file mode 100644
index 00000000..661fd423
--- /dev/null
+++ b/js_interop_gen/test/integration/idl/maplike_input.idl
@@ -0,0 +1,9 @@
+[Exposed=Window]
+interface MyMaplike {
+  readonly maplike<DOMString, DOMString>;
+};
+
+[Exposed=Window]
+interface MyReadWriteMaplike {
+  maplike<DOMString, DOMString>;
+};
diff --git a/web/lib/src/dom/css_highlight_api.dart b/web/lib/src/dom/css_highlight_api.dart
index d5ac85d7..49146178 100644
--- a/web/lib/src/dom/css_highlight_api.dart
+++ b/web/lib/src/dom/css_highlight_api.dart
@@ -13,6 +13,7 @@
 @JS()
 library;
 
+import 'dart:collection';
 import 'dart:js_interop';
 
 import 'dom.dart';
@@ -96,4 +97,56 @@ extension type Highlight._(JSObject _) implements JSObject {
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/HighlightRegistry).
-extension type HighlightRegistry._(JSObject _) implements JSObject {}
+extension type HighlightRegistry._(JSObject _) implements JSObject {
+  @JS()
+  external Highlight? get(JSString key);
+  @JS()
+  external bool has(JSString key);
+  @JS()
+  external void set(JSString key, Highlight value);
+  @JS()
+  external bool delete(JSString key);
+  @JS()
+  external void clear();
+  @JS()
+  external JSIterator<JSString> keys();
+  Map<String, Highlight> get asMap => _HighlightRegistryMapView(this);
+}
+
+class _HighlightRegistryMapView extends MapBase<String, Highlight> {
+  _HighlightRegistryMapView(this._jsObject);
+
+  final HighlightRegistry _jsObject;
+
+  @override
+  Highlight? operator [](Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key.toJS);
+    if (value == null) return null;
+    return value;
+  }
+
+  @override
+  void operator []=(String key, Highlight value) {
+    _jsObject.set(key.toJS, value);
+  }
+
+  @override
+  void clear() {
+    _jsObject.clear();
+  }
+
+  @override
+  Iterable<String> get keys {
+    return _jsObject.keys().toDartIterable.map((e) => e.toDart);
+  }
+
+  @override
+  Highlight? remove(Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key.toJS);
+    _jsObject.delete(key.toJS);
+    if (value == null) return null;
+    return value;
+  }
+}
diff --git a/web/lib/src/dom/css_typed_om.dart b/web/lib/src/dom/css_typed_om.dart
index 8cbbeba5..2d93de90 100644
--- a/web/lib/src/dom/css_typed_om.dart
+++ b/web/lib/src/dom/css_typed_om.dart
@@ -13,6 +13,7 @@
 @JS()
 library;
 
+import 'dart:collection';
 import 'dart:js_interop';
 
 import 'geometry.dart';
@@ -68,7 +69,8 @@ extension type CSSStyleValue._(JSObject _) implements JSObject {
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/StylePropertyMapReadOnly).
-extension type StylePropertyMapReadOnly._(JSObject _) implements JSObject {
+extension type StylePropertyMapReadOnly._(JSObject _)
+    implements JSObject, JSIterable<JSArray<JSAny>> {
   /// The **`get()`** method of the
   /// [StylePropertyMapReadOnly] interface returns a [CSSStyleValue]
   /// object for the first value of the specified property.
@@ -88,6 +90,37 @@ extension type StylePropertyMapReadOnly._(JSObject _) implements JSObject {
   /// [StylePropertyMapReadOnly] interface returns an unsigned long integer
   /// containing the size of the `StylePropertyMapReadOnly` object.
   external int get size;
+  Iterable<({String key, JSArray value})> get toDart => toDartIterable.map(
+    (e) => (
+      key: (e.toDart[0] as JSString).toDart,
+      value: (e.toDart[1] as JSArray),
+    ),
+  );
+
+  @JS()
+  external JSIterator<JSString> keys();
+  Map<String, JSArray<CSSStyleValue>> get asMap =>
+      _StylePropertyMapReadOnlyMapView(this);
+}
+
+class _StylePropertyMapReadOnlyMapView
+    extends UnmodifiableMapBase<String, JSArray<CSSStyleValue>> {
+  _StylePropertyMapReadOnlyMapView(this._jsObject);
+
+  final StylePropertyMapReadOnly _jsObject;
+
+  @override
+  JSArray<CSSStyleValue>? operator [](Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key);
+    if (value == null) return null;
+    return _jsObject.getAll(key);
+  }
+
+  @override
+  Iterable<String> get keys {
+    return _jsObject.keys().toDartIterable.map((e) => e.toDart);
+  }
 }
 
 /// The **`StylePropertyMap`** interface of the
@@ -130,6 +163,52 @@ extension type StylePropertyMap._(JSObject _)
   /// The **`clear()`** method of the [StylePropertyMap]
   /// interface removes all declarations in the `StylePropertyMap`.
   external void clear();
+  @JS()
+  external JSIterator<JSString> keys();
+  Map<String, JSArray<CSSStyleValue>> get asMap =>
+      _StylePropertyMapMapView(this);
+}
+
+class _StylePropertyMapMapView extends MapBase<String, JSArray<CSSStyleValue>> {
+  _StylePropertyMapMapView(this._jsObject);
+
+  final StylePropertyMap _jsObject;
+
+  @override
+  JSArray<CSSStyleValue>? operator [](Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key);
+    if (value == null) return null;
+    return _jsObject.getAll(key);
+  }
+
+  @override
+  void operator []=(String key, JSArray<CSSStyleValue> value) {
+    _jsObject.set(key, value);
+  }
+
+  @override
+  void clear() {
+    final keys = _jsObject.keys().toDartIterable.toList();
+    for (final k in keys) {
+      _jsObject.delete(k.toDart);
+    }
+  }
+
+  @override
+  Iterable<String> get keys {
+    return _jsObject.keys().toDartIterable.map((e) => e.toDart);
+  }
+
+  @override
+  JSArray<CSSStyleValue>? remove(Object? key) {
+    if (key is! String) return null;
+    final values = _jsObject.getAll(key);
+    // ignore: prefer_is_empty
+    if (values.length == 0) return null;
+    _jsObject.delete(key);
+    return values;
+  }
 }
 
 /// The **`CSSUnparsedValue`** interface of the
@@ -146,7 +225,7 @@ extension type StylePropertyMap._(JSObject _)
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/CSSUnparsedValue).
 extension type CSSUnparsedValue._(JSObject _)
-    implements CSSStyleValue, JSObject {
+    implements CSSStyleValue, JSObject, JSIterable<CSSUnparsedSegment> {
   external factory CSSUnparsedValue(JSArray<CSSUnparsedSegment> members);
 
   external CSSUnparsedSegment operator [](int index);
@@ -155,6 +234,7 @@ extension type CSSUnparsedValue._(JSObject _)
   /// The **`length`** read-only property of the
   /// [CSSUnparsedValue] interface returns the number of items in the object.
   external int get length;
+  Iterable<CSSUnparsedSegment> get toDart => toDartIterable;
 }
 
 /// The **`CSSVariableReferenceValue`** interface of the
@@ -517,13 +597,15 @@ extension type CSSMathClamp._(JSObject _) implements CSSMathValue, JSObject {
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/CSSNumericArray).
-extension type CSSNumericArray._(JSObject _) implements JSObject {
+extension type CSSNumericArray._(JSObject _)
+    implements JSObject, JSIterable<CSSNumericValue> {
   external CSSNumericValue operator [](int index);
 
   /// The read-only **`length`** property of the
   /// [CSSNumericArray] interface returns the number of
   /// [CSSNumericValue] objects in the list.
   external int get length;
+  Iterable<CSSNumericValue> get toDart => toDartIterable;
 }
 
 /// The **`CSSTransformValue`** interface of the
@@ -535,7 +617,7 @@ extension type CSSNumericArray._(JSObject _) implements JSObject {
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/CSSTransformValue).
 extension type CSSTransformValue._(JSObject _)
-    implements CSSStyleValue, JSObject {
+    implements CSSStyleValue, JSObject, JSIterable<CSSTransformComponent> {
   external factory CSSTransformValue(JSArray<CSSTransformComponent> transforms);
 
   external CSSTransformComponent operator [](int index);
@@ -559,6 +641,7 @@ extension type CSSTransformValue._(JSObject _)
   /// which
   /// case it returns false.
   external bool get is2D;
+  Iterable<CSSTransformComponent> get toDart => toDartIterable;
 }
 
 /// The **`CSSTransformComponent`** interface of the
diff --git a/web/lib/src/dom/dom.dart b/web/lib/src/dom/dom.dart
index 43959fa6..b17e97ae 100644
--- a/web/lib/src/dom/dom.dart
+++ b/web/lib/src/dom/dom.dart
@@ -671,7 +671,7 @@ extension type AbortSignal._(JSObject _) implements EventTarget, JSObject {
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/NodeList).
-extension type NodeList._(JSObject _) implements JSObject {
+extension type NodeList._(JSObject _) implements JSObject, JSIterable<Node> {
   /// Returns a node from a
   /// [`NodeList`](https://developer.mozilla.org/en-US/docs/Web/API/NodeList) by
   /// index. This method
@@ -688,6 +688,7 @@ extension type NodeList._(JSObject _) implements JSObject {
   /// The **`NodeList.length`** property returns the number of items
   /// in a [NodeList].
   external int get length;
+  Iterable<Node> get toDart => toDartIterable;
 }
 
 /// The **`HTMLCollection`** interface represents a generic collection
@@ -5379,7 +5380,8 @@ extension type TreeWalker._(JSObject _) implements JSObject {
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/DOMTokenList).
-extension type DOMTokenList._(JSObject _) implements JSObject {
+extension type DOMTokenList._(JSObject _)
+    implements JSObject, JSIterable<JSString> {
   /// The **`item()`** method of the [DOMTokenList] interface returns an item in
   /// the list,
   /// determined by its position in the list, its index.
@@ -5441,6 +5443,7 @@ extension type DOMTokenList._(JSObject _) implements JSObject {
   /// string, or clears and sets the list to the given value.
   external String get value;
   external set value(String value);
+  Iterable<String> get toDart => toDartIterable.map((e) => e.toDart);
 }
 
 /// The **`XPathResult`** interface represents the results generated by
diff --git a/web/lib/src/dom/encrypted_media.dart b/web/lib/src/dom/encrypted_media.dart
index edd50be8..17ab3eec 100644
--- a/web/lib/src/dom/encrypted_media.dart
+++ b/web/lib/src/dom/encrypted_media.dart
@@ -13,6 +13,7 @@
 @JS()
 library;
 
+import 'dart:collection';
 import 'dart:js_interop';
 
 import 'dom.dart';
@@ -234,7 +235,8 @@ extension type MediaKeySession._(JSObject _) implements EventTarget, JSObject {
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/MediaKeyStatusMap).
-extension type MediaKeyStatusMap._(JSObject _) implements JSObject {
+extension type MediaKeyStatusMap._(JSObject _)
+    implements JSObject, JSIterable<JSArray<JSAny>> {
   /// The **`has()`** method of the
   /// [MediaKeyStatusMap] interface returns a `Boolean`, asserting
   /// whether a value has been associated with the given key.
@@ -252,6 +254,38 @@ extension type MediaKeyStatusMap._(JSObject _) implements JSObject {
   /// the [MediaKeyStatusMap] interface returns the number of key/value paIrs
   /// in the status map.
   external int get size;
+  Iterable<({BufferSource key, String value})> get toDart => toDartIterable.map(
+    (e) => (
+      key: (e.toDart[0] as BufferSource),
+      value: (e.toDart[1] as JSString).toDart,
+    ),
+  );
+
+  @JS()
+  external JSIterator<BufferSource> keys();
+  Map<BufferSource, MediaKeyStatus> get asMap =>
+      _MediaKeyStatusMapMapView(this);
+}
+
+class _MediaKeyStatusMapMapView
+    extends UnmodifiableMapBase<BufferSource, MediaKeyStatus> {
+  _MediaKeyStatusMapMapView(this._jsObject);
+
+  final MediaKeyStatusMap _jsObject;
+
+  @override
+  MediaKeyStatus? operator [](Object? key) {
+    if (key == null || !(key as JSAny).isA<JSObject>()) return null;
+    final jsKey = key as JSObject;
+    final value = _jsObject.get(jsKey);
+    if (value == null) return null;
+    return value;
+  }
+
+  @override
+  Iterable<BufferSource> get keys {
+    return _jsObject.keys().toDartIterable;
+  }
 }
 
 /// The **`MediaKeyMessageEvent`** interface of the
diff --git a/web/lib/src/dom/event_timing.dart b/web/lib/src/dom/event_timing.dart
index e99042e7..64dac03e 100644
--- a/web/lib/src/dom/event_timing.dart
+++ b/web/lib/src/dom/event_timing.dart
@@ -13,6 +13,7 @@
 @JS()
 library;
 
+import 'dart:collection';
 import 'dart:js_interop';
 
 import 'dom.dart';
@@ -69,4 +70,31 @@ extension type PerformanceEventTiming._(JSObject _)
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/EventCounts).
-extension type EventCounts._(JSObject _) implements JSObject {}
+extension type EventCounts._(JSObject _) implements JSObject {
+  @JS()
+  external JSNumber? get(JSString key);
+  @JS()
+  external bool has(JSString key);
+  @JS()
+  external JSIterator<JSString> keys();
+  Map<String, int> get asMap => _EventCountsMapView(this);
+}
+
+class _EventCountsMapView extends UnmodifiableMapBase<String, int> {
+  _EventCountsMapView(this._jsObject);
+
+  final EventCounts _jsObject;
+
+  @override
+  int? operator [](Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key.toJS);
+    if (value == null) return null;
+    return value.toDartDouble.toInt();
+  }
+
+  @override
+  Iterable<String> get keys {
+    return _jsObject.keys().toDartIterable.map((e) => e.toDart);
+  }
+}
diff --git a/web/lib/src/dom/fetch.dart b/web/lib/src/dom/fetch.dart
index 9a3c612b..65366bab 100644
--- a/web/lib/src/dom/fetch.dart
+++ b/web/lib/src/dom/fetch.dart
@@ -15,6 +15,7 @@
 @JS()
 library;
 
+import 'dart:collection';
 import 'dart:js_interop';
 
 import 'attribution_reporting_api.dart';
@@ -73,7 +74,8 @@ typedef ResponseType = String;
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/Headers).
-extension type Headers._(JSObject _) implements JSObject {
+extension type Headers._(JSObject _)
+    implements JSObject, JSIterable<JSArray<JSAny>> {
   external factory Headers([HeadersInit init]);
 
   /// The **`append()`** method of the [Headers]
@@ -150,6 +152,57 @@ extension type Headers._(JSObject _) implements JSObject {
   /// headers include the
   /// and .
   external void set(String name, String value);
+  Iterable<({String key, String value})> get toDart => toDartIterable.map(
+    (e) => (
+      key: (e.toDart[0] as JSString).toDart,
+      value: (e.toDart[1] as JSString).toDart,
+    ),
+  );
+
+  @JS()
+  external JSIterator<JSString> keys();
+  Map<String, String> get asMap => _HeadersMapView(this);
+}
+
+class _HeadersMapView extends MapBase<String, String> {
+  _HeadersMapView(this._jsObject);
+
+  final Headers _jsObject;
+
+  @override
+  String? operator [](Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key);
+    if (value == null) return null;
+    return value;
+  }
+
+  @override
+  void operator []=(String key, String value) {
+    _jsObject.set(key, value);
+  }
+
+  @override
+  void clear() {
+    final keys = _jsObject.keys().toDartIterable.toList();
+    for (final k in keys) {
+      _jsObject.delete(k.toDart);
+    }
+  }
+
+  @override
+  Iterable<String> get keys {
+    return _jsObject.keys().toDartIterable.map((e) => e.toDart);
+  }
+
+  @override
+  String? remove(Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key);
+    _jsObject.delete(key);
+    if (value == null) return null;
+    return value;
+  }
 }
 
 /// The **`Request`** interface of the
diff --git a/web/lib/src/dom/url.dart b/web/lib/src/dom/url.dart
index 960ae176..740f2071 100644
--- a/web/lib/src/dom/url.dart
+++ b/web/lib/src/dom/url.dart
@@ -13,6 +13,7 @@
 @JS()
 library;
 
+import 'dart:collection';
 import 'dart:js_interop';
 
 /// The **`URL`** interface is used to parse, construct, normalize, and encode .
@@ -286,7 +287,8 @@ extension type URL._(JSObject _) implements JSObject {
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/URLSearchParams).
-extension type URLSearchParams._(JSObject _) implements JSObject {
+extension type URLSearchParams._(JSObject _)
+    implements JSObject, JSIterable<JSArray<JSAny>> {
   external factory URLSearchParams([JSAny init]);
 
   /// The **`append()`** method of the [URLSearchParams]
@@ -350,4 +352,55 @@ extension type URLSearchParams._(JSObject _) implements JSObject {
   /// The **`size`** read-only property of the [URLSearchParams] interface
   /// indicates the total number of search parameter entries.
   external int get size;
+  Iterable<({String key, String value})> get toDart => toDartIterable.map(
+    (e) => (
+      key: (e.toDart[0] as JSString).toDart,
+      value: (e.toDart[1] as JSString).toDart,
+    ),
+  );
+
+  @JS()
+  external JSIterator<JSString> keys();
+  Map<String, String> get asMap => _URLSearchParamsMapView(this);
+}
+
+class _URLSearchParamsMapView extends MapBase<String, String> {
+  _URLSearchParamsMapView(this._jsObject);
+
+  final URLSearchParams _jsObject;
+
+  @override
+  String? operator [](Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key);
+    if (value == null) return null;
+    return value;
+  }
+
+  @override
+  void operator []=(String key, String value) {
+    _jsObject.set(key, value);
+  }
+
+  @override
+  void clear() {
+    final keys = _jsObject.keys().toDartIterable.toList();
+    for (final k in keys) {
+      _jsObject.delete(k.toDart);
+    }
+  }
+
+  @override
+  Iterable<String> get keys {
+    return _jsObject.keys().toDartIterable.map((e) => e.toDart);
+  }
+
+  @override
+  String? remove(Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key);
+    _jsObject.delete(key);
+    if (value == null) return null;
+    return value;
+  }
 }
diff --git a/web/lib/src/dom/webaudio.dart b/web/lib/src/dom/webaudio.dart
index d1a1c49f..97286ea4 100644
--- a/web/lib/src/dom/webaudio.dart
+++ b/web/lib/src/dom/webaudio.dart
@@ -13,6 +13,7 @@
 @JS()
 library;
 
+import 'dart:collection';
 import 'dart:js_interop';
 
 import 'dom.dart';
@@ -3496,7 +3497,34 @@ extension type AudioWorkletGlobalScope._(JSObject _)
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/AudioParamMap).
-extension type AudioParamMap._(JSObject _) implements JSObject {}
+extension type AudioParamMap._(JSObject _) implements JSObject {
+  @JS()
+  external AudioParam? get(JSString key);
+  @JS()
+  external bool has(JSString key);
+  @JS()
+  external JSIterator<JSString> keys();
+  Map<String, AudioParam> get asMap => _AudioParamMapMapView(this);
+}
+
+class _AudioParamMapMapView extends UnmodifiableMapBase<String, AudioParam> {
+  _AudioParamMapMapView(this._jsObject);
+
+  final AudioParamMap _jsObject;
+
+  @override
+  AudioParam? operator [](Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key.toJS);
+    if (value == null) return null;
+    return value;
+  }
+
+  @override
+  Iterable<String> get keys {
+    return _jsObject.keys().toDartIterable.map((e) => e.toDart);
+  }
+}
 
 /// > [!NOTE]
 /// > Although the interface is available outside
diff --git a/web/lib/src/dom/webmidi.dart b/web/lib/src/dom/webmidi.dart
index ee054cc4..aa7fb9b5 100644
--- a/web/lib/src/dom/webmidi.dart
+++ b/web/lib/src/dom/webmidi.dart
@@ -13,6 +13,7 @@
 @JS()
 library;
 
+import 'dart:collection';
 import 'dart:js_interop';
 
 import 'dom.dart';
@@ -44,7 +45,34 @@ extension type MIDIOptions._(JSObject _) implements JSObject {
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/MIDIInputMap).
-extension type MIDIInputMap._(JSObject _) implements JSObject {}
+extension type MIDIInputMap._(JSObject _) implements JSObject {
+  @JS()
+  external MIDIInput? get(JSString key);
+  @JS()
+  external bool has(JSString key);
+  @JS()
+  external JSIterator<JSString> keys();
+  Map<String, MIDIInput> get asMap => _MIDIInputMapMapView(this);
+}
+
+class _MIDIInputMapMapView extends UnmodifiableMapBase<String, MIDIInput> {
+  _MIDIInputMapMapView(this._jsObject);
+
+  final MIDIInputMap _jsObject;
+
+  @override
+  MIDIInput? operator [](Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key.toJS);
+    if (value == null) return null;
+    return value;
+  }
+
+  @override
+  Iterable<String> get keys {
+    return _jsObject.keys().toDartIterable.map((e) => e.toDart);
+  }
+}
 
 /// The **`MIDIOutputMap`** read-only interface of the
 /// [Web MIDI API](https://developer.mozilla.org/en-US/docs/Web/API/Web_MIDI_API)
@@ -59,7 +87,34 @@ extension type MIDIInputMap._(JSObject _) implements JSObject {}
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/MIDIOutputMap).
-extension type MIDIOutputMap._(JSObject _) implements JSObject {}
+extension type MIDIOutputMap._(JSObject _) implements JSObject {
+  @JS()
+  external MIDIOutput? get(JSString key);
+  @JS()
+  external bool has(JSString key);
+  @JS()
+  external JSIterator<JSString> keys();
+  Map<String, MIDIOutput> get asMap => _MIDIOutputMapMapView(this);
+}
+
+class _MIDIOutputMapMapView extends UnmodifiableMapBase<String, MIDIOutput> {
+  _MIDIOutputMapMapView(this._jsObject);
+
+  final MIDIOutputMap _jsObject;
+
+  @override
+  MIDIOutput? operator [](Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key.toJS);
+    if (value == null) return null;
+    return value;
+  }
+
+  @override
+  Iterable<String> get keys {
+    return _jsObject.keys().toDartIterable.map((e) => e.toDart);
+  }
+}
 
 /// The **`MIDIAccess`** interface of the
 /// [Web MIDI API](https://developer.mozilla.org/en-US/docs/Web/API/Web_MIDI_API)
diff --git a/web/lib/src/dom/webrtc.dart b/web/lib/src/dom/webrtc.dart
index f38fdd81..9c1303d4 100644
--- a/web/lib/src/dom/webrtc.dart
+++ b/web/lib/src/dom/webrtc.dart
@@ -13,6 +13,7 @@
 @JS()
 library;
 
+import 'dart:collection';
 import 'dart:js_interop';
 
 import 'dom.dart';
@@ -2303,7 +2304,34 @@ extension type RTCDTMFToneChangeEventInit._(JSObject _)
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/RTCStatsReport).
-extension type RTCStatsReport._(JSObject _) implements JSObject {}
+extension type RTCStatsReport._(JSObject _) implements JSObject {
+  @JS()
+  external JSObject? get(JSString key);
+  @JS()
+  external bool has(JSString key);
+  @JS()
+  external JSIterator<JSString> keys();
+  Map<String, JSObject> get asMap => _RTCStatsReportMapView(this);
+}
+
+class _RTCStatsReportMapView extends UnmodifiableMapBase<String, JSObject> {
+  _RTCStatsReportMapView(this._jsObject);
+
+  final RTCStatsReport _jsObject;
+
+  @override
+  JSObject? operator [](Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key.toJS);
+    if (value == null) return null;
+    return value;
+  }
+
+  @override
+  Iterable<String> get keys {
+    return _jsObject.keys().toDartIterable.map((e) => e.toDart);
+  }
+}
 
 /// The **`RTCError`** interface describes an error which has occurred while
 /// handling
diff --git a/web/lib/src/dom/webxr_hand_input.dart b/web/lib/src/dom/webxr_hand_input.dart
index a8a4c047..057706d2 100644
--- a/web/lib/src/dom/webxr_hand_input.dart
+++ b/web/lib/src/dom/webxr_hand_input.dart
@@ -28,7 +28,15 @@ typedef XRHandJoint = String;
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/XRHand).
-extension type XRHand._(JSObject _) implements JSObject {}
+extension type XRHand._(JSObject _)
+    implements JSObject, JSIterable<JSArray<JSAny>> {
+  Iterable<({String key, XRJointSpace value})> get toDart => toDartIterable.map(
+    (e) => (
+      key: (e.toDart[0] as JSString).toDart,
+      value: (e.toDart[1] as XRJointSpace),
+    ),
+  );
+}
 
 /// The **`XRJointSpace`** interface is an [XRSpace] and represents the position
 /// and orientation of an [XRHand] joint.
diff --git a/web/lib/src/dom/xhr.dart b/web/lib/src/dom/xhr.dart
index 621f9bda..0155432f 100644
--- a/web/lib/src/dom/xhr.dart
+++ b/web/lib/src/dom/xhr.dart
@@ -14,6 +14,7 @@
 @JS()
 library;
 
+import 'dart:collection';
 import 'dart:js_interop';
 
 import 'dom.dart';
@@ -515,7 +516,8 @@ extension type XMLHttpRequest._(JSObject _)
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/FormData).
-extension type FormData._(JSObject _) implements JSObject {
+extension type FormData._(JSObject _)
+    implements JSObject, JSIterable<JSArray<JSAny>> {
   external factory FormData([HTMLFormElement form, HTMLElement? submitter]);
 
   /// The **`append()`** method of the [FormData] interface appends a new value
@@ -556,6 +558,55 @@ extension type FormData._(JSObject _) implements JSObject {
   /// values with the new one, whereas `append()` will append the new value onto
   /// the end of the existing set of values.
   external void set(String name, JSAny blobValueOrValue, [String filename]);
+  Iterable<({String key, FormDataEntryValue value})> get toDart =>
+      toDartIterable.map(
+        (e) => (key: (e.toDart[0] as JSString).toDart, value: e.toDart[1]),
+      );
+
+  @JS()
+  external JSIterator<JSString> keys();
+  Map<String, FormDataEntryValue> get asMap => _FormDataMapView(this);
+}
+
+class _FormDataMapView extends MapBase<String, FormDataEntryValue> {
+  _FormDataMapView(this._jsObject);
+
+  final FormData _jsObject;
+
+  @override
+  FormDataEntryValue? operator [](Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key);
+    if (value == null) return null;
+    return value;
+  }
+
+  @override
+  void operator []=(String key, FormDataEntryValue value) {
+    _jsObject.set(key, value);
+  }
+
+  @override
+  void clear() {
+    final keys = _jsObject.keys().toDartIterable.toList();
+    for (final k in keys) {
+      _jsObject.delete(k.toDart);
+    }
+  }
+
+  @override
+  Iterable<String> get keys {
+    return _jsObject.keys().toDartIterable.map((e) => e.toDart);
+  }
+
+  @override
+  FormDataEntryValue? remove(Object? key) {
+    if (key is! String) return null;
+    final value = _jsObject.get(key);
+    _jsObject.delete(key);
+    if (value == null) return null;
+    return value;
+  }
 }
 
 /// The **`ProgressEvent`** interface represents events measuring progress of an
diff --git a/web/pubspec.yaml b/web/pubspec.yaml
index e8a9a696..43b0246f 100644
--- a/web/pubspec.yaml
+++ b/web/pubspec.yaml
@@ -4,7 +4,7 @@ description: Lightweight browser API bindings built around JS interop.
 repository: https://github.com/dart-lang/web
 
 environment:
-  sdk: ^3.10.0
+  sdk: ^3.12.0-0
 
 dev_dependencies:
   dart_flutter_team_lints: ^3.0.0
diff --git a/web/test/smoke_test.dart b/web/test/smoke_test.dart
index 3a2eb667..1ffa7815 100644
--- a/web/test/smoke_test.dart
+++ b/web/test/smoke_test.dart
@@ -79,4 +79,153 @@ void main() {
         );
     }
   });
+
+  test('URLSearchParams toDart works as expected.', () {
+    final params = URLSearchParams('a=1&b=2'.toJS);
+    final list = params.toDart.toList();
+    expect(list.length, equals(2));
+    expect(list[0].key, equals('a'));
+    expect(list[0].value, equals('1'));
+    expect(list[1].key, equals('b'));
+    expect(list[1].value, equals('2'));
+  });
+
+  test('FormData toDart works as expected.', () {
+    final form = FormData();
+    form.append('a', '1'.toJS);
+    form.append('b', '2'.toJS);
+    final list = form.toDart.toList();
+    expect(list.length, equals(2));
+    expect(list[0].key, equals('a'));
+    expect((list[0].value as JSString).toDart, equals('1'));
+    expect(list[1].key, equals('b'));
+    expect((list[1].value as JSString).toDart, equals('2'));
+  });
+
+  test('NodeList toDart works as expected.', () {
+    final div = document.createElement('div') as HTMLDivElement;
+    final span1 = document.createElement('span');
+    final span2 = document.createElement('span');
+    div.appendChild(span1);
+    div.appendChild(span2);
+    final list = div.childNodes.toDart.toList();
+    expect(list.length, equals(2));
+    expect(list[0], equals(span1));
+    expect(list[1], equals(span2));
+  });
+
+  test('URLSearchParams asMap', () {
+    final params = URLSearchParams('a=1&b=2'.toJS);
+    final map = params.asMap;
+
+    // Read operations
+    expect(map['a'], '1');
+    expect(map['b'], '2');
+    expect(map['c'], null);
+    expect(map.containsKey('a'), true);
+    expect(map.containsKey('c'), false);
+    expect(map.containsValue('1'), true);
+    expect(map.containsValue('3'), false);
+    expect(map.length, 2);
+    expect(map.isEmpty, false);
+    expect(map.isNotEmpty, true);
+
+    // Keys and values
+    expect(map.keys.toList(), containsAll(['a', 'b']));
+    expect(map.values.toList(), containsAll(['1', '2']));
+
+    // Write operations
+    map['a'] = '3';
+    expect(map['a'], '3');
+    expect(params.get('a'), '3');
+
+    map['c'] = '4';
+    expect(map['c'], '4');
+    expect(params.get('c'), '4');
+    expect(map.length, 3);
+
+    // Remove
+    expect(map.remove('b'), '2');
+    expect(map.containsKey('b'), false);
+    expect(params.has('b'), false);
+    expect(map.length, 2);
+
+    // Remove non-existent
+    expect(map.remove('d'), null);
+
+    // Clear
+    map.clear();
+    expect(map.isEmpty, true);
+    expect(map.length, 0);
+    expect(params.get('a'), null);
+
+    // Sanity checks on Object? types for map operations
+    map['a'] = '1';
+    final dummyJsObject = JSObject();
+    final dummyDartObject = Object();
+
+    // operator [] should safely return null for non-Strings
+    // ignore: collection_methods_unrelated_type
+    expect(map[dummyJsObject], isNull);
+    expect(map[dummyDartObject], isNull);
+    // ignore: collection_methods_unrelated_type
+    expect(map[123], isNull);
+
+    // remove should safely return null for non-Strings
+    // ignore: collection_methods_unrelated_type
+    expect(map.remove(dummyJsObject), isNull);
+    expect(map.remove(dummyDartObject), isNull);
+    // ignore: collection_methods_unrelated_type
+    expect(map.remove(123), isNull);
+
+    // Ensure actual element wasn't removed accidentally
+    expect(map['a'], '1');
+  });
+
+  test('StylePropertyMap asMap', () {
+    final div = document.createElement('div') as HTMLDivElement;
+    div.style.color = 'blue';
+    final map = div.attributeStyleMap.asMap;
+
+    // Read operations
+    expect(map.containsKey('color'), true);
+    final values = map['color'];
+    expect(values, isNotNull);
+    expect(values!.toDart.length, 1);
+
+    // Remove operation
+    final removed = map.remove('color');
+    expect(removed, isNotNull);
+    expect(removed!.toDart.length, 1);
+    expect(map.containsKey('color'), false);
+    expect(div.style.color, equals(''));
+
+    // Remove non-existent
+    final removedAgain = map.remove('color');
+    expect(removedAgain, isNull);
+  });
+
+  test('EventCounts', () {
+    final performance = window.performance;
+    expect(performance, isNotNull);
+
+    final eventCounts = performance.eventCounts;
+    expect(eventCounts, isNotNull);
+
+    final map = eventCounts.asMap;
+
+    // We cannot easily populate EventCounts, but we can verify it is a Map
+    // and that it behaves as a read-only map.
+    expect(map, isA<Map<String, int>>());
+
+    // Should not throw on access.
+    expect(() => map.length, returnsNormally);
+    expect(() => map.isEmpty, returnsNormally);
+    expect(() => map.keys, returnsNormally);
+
+    // Mutating operations should throw UnsupportedError.
+    expect(() => map['click'] = 1, throwsUnsupportedError);
+    expect(map.clear, throwsUnsupportedError);
+    expect(() => map.remove('click'), throwsUnsupportedError);
+  });
 }
diff --git a/web_generator/pubspec.yaml b/web_generator/pubspec.yaml
index 95f3a884..e7cfd8f7 100644
--- a/web_generator/pubspec.yaml
+++ b/web_generator/pubspec.yaml
@@ -4,7 +4,7 @@ description: Generator scripts specific to package:web.
 repository: https://github.com/dart-lang/web
 
 environment:
-  sdk: ^3.10.0
+  sdk: ^3.12.0-0
 
 dependencies:
   args: ^2.5.0