feat(chain, zipIterable, enumerate): add lazy iterator utilities

benchmarks/bundle-size/camelCase.spec.ts

@@ -14,6 +14,6 @@ describe('camelCase bundle size', () => {
 
   it('es-toolkit/compat', async () => {
     const bundleSize = await getBundleSize('es-toolkit/compat', 'camelCase');
-    expect(bundleSize).toMatchInlineSnapshot(`650`);
+    expect(bundleSize).toMatchInlineSnapshot(`1287`);
   });
 });

benchmarks/bundle-size/chain.spec.ts

@@ -0,0 +1,14 @@
+import { describe, expect, it } from 'vitest';
+import { getBundleSize } from './utils/getBundleSize';
+
+describe('chain bundle size', () => {
+  it('es-toolkit', async () => {
+    const bundleSize = await getBundleSize('es-toolkit/iterator', 'chain');
+    expect(bundleSize).toMatchInlineSnapshot(`82`);
+  });
+
+  it('itertools', async () => {
+    const bundleSize = await getBundleSize('itertools', 'chain');
+    expect(bundleSize).toMatchInlineSnapshot(`252`);
+  });
+});

benchmarks/bundle-size/clone.spec.ts

@@ -9,7 +9,7 @@ describe('clone bundle size', () => {
 
   it('es-toolkit', async () => {
     const bundleSize = await getBundleSize('es-toolkit', 'clone');
-    expect(bundleSize).toMatchInlineSnapshot(`866`);
+    expect(bundleSize).toMatchInlineSnapshot(`1001`);
   });
 
   it('es-toolkit/compat', async () => {

benchmarks/bundle-size/cloneDeep.spec.ts

@@ -9,11 +9,11 @@ describe('cloneDeep bundle size', () => {
 
   it('es-toolkit', async () => {
     const bundleSize = await getBundleSize('es-toolkit', 'cloneDeep');
-    expect(bundleSize).toMatchInlineSnapshot(`3171`);
+    expect(bundleSize).toMatchInlineSnapshot(`3200`);
   });
 
   it('es-toolkit/compat', async () => {
     const bundleSize = await getBundleSize('es-toolkit/compat', 'cloneDeep');
-    expect(bundleSize).toMatchInlineSnapshot(`3522`);
+    expect(bundleSize).toMatchInlineSnapshot(`3640`);
   });
 });

benchmarks/bundle-size/enumerate.spec.ts

@@ -0,0 +1,14 @@
+import { describe, expect, it } from 'vitest';
+import { getBundleSize } from './utils/getBundleSize';
+
+describe('enumerate bundle size', () => {
+  it('es-toolkit', async () => {
+    const bundleSize = await getBundleSize('es-toolkit/iterator', 'enumerate');
+    expect(bundleSize).toMatchInlineSnapshot(`212`);
+  });
+
+  it('@fxts/core', async () => {
+    const bundleSize = await getBundleSize('@fxts/core', 'zipWithIndex');
+    expect(bundleSize).toMatchInlineSnapshot(`2710`);
+  });
+});

benchmarks/bundle-size/find.spec.ts

@@ -9,6 +9,6 @@ describe('find bundle size', () => {
 
   it('es-toolkit/compat', async () => {
     const bundleSize = await getBundleSize('es-toolkit/compat', 'find');
-    expect(bundleSize).toMatchInlineSnapshot(`7763`);
+    expect(bundleSize).toMatchInlineSnapshot(`7887`);
   });
 });

benchmarks/bundle-size/findKey.spec.ts

@@ -14,6 +14,6 @@ describe('findKey bundle size', () => {
 
   it('es-toolkit/compat', async () => {
     const bundleSize = await getBundleSize('es-toolkit/compat', 'findKey');
-    expect(bundleSize).toMatchInlineSnapshot(`7688`);
+    expect(bundleSize).toMatchInlineSnapshot(`7812`);
   });
 });

benchmarks/bundle-size/lastIndexOf.spec.ts

@@ -4,7 +4,7 @@ import { getBundleSize } from './utils/getBundleSize';
 describe('lastIndexOf bundle size', () => {
   it('lodash-es', async () => {
     const bundleSize = await getBundleSize('lodash-es', 'lastIndexOf');
-    expect(bundleSize).toMatchInlineSnapshot(`1586`);
+    expect(bundleSize).toMatchInlineSnapshot(`2481`);
   });
 
   it('es-toolkit/compat', async () => {

benchmarks/bundle-size/mapKeys.spec.ts

@@ -14,6 +14,6 @@ describe('mapKeys bundle size', () => {
 
   it('es-toolkit/compat', async () => {
     const bundleSize = await getBundleSize('es-toolkit/compat', 'mapKeys');
-    expect(bundleSize).toMatchInlineSnapshot(`7701`);
+    expect(bundleSize).toMatchInlineSnapshot(`7825`);
   });
 });

benchmarks/bundle-size/mapValues.spec.ts

@@ -14,6 +14,6 @@ describe('mapValues bundle size', () => {
 
   it('es-toolkit/compat', async () => {
     const bundleSize = await getBundleSize('es-toolkit/compat', 'mapValues');
-    expect(bundleSize).toMatchInlineSnapshot(`7701`);
+    expect(bundleSize).toMatchInlineSnapshot(`7825`);
   });
 });

benchmarks/bundle-size/merge.spec.ts

@@ -9,11 +9,11 @@ describe('merge bundle size', () => {
 
   it('es-toolkit', async () => {
     const bundleSize = await getBundleSize('es-toolkit', 'merge');
-    expect(bundleSize).toMatchInlineSnapshot(`521`);
+    expect(bundleSize).toMatchInlineSnapshot(`542`);
   });
 
   it('es-toolkit/compat', async () => {
     const bundleSize = await getBundleSize('es-toolkit/compat', 'merge');
-    expect(bundleSize).toMatchInlineSnapshot(`5721`);
+    expect(bundleSize).toMatchInlineSnapshot(`6206`);
   });
 });

benchmarks/bundle-size/mergeWith.spec.ts

@@ -9,11 +9,11 @@ describe('mergeWith bundle size', () => {
 
   it('es-toolkit', async () => {
     const bundleSize = await getBundleSize('es-toolkit', 'mergeWith');
-    expect(bundleSize).toMatchInlineSnapshot(`368`);
+    expect(bundleSize).toMatchInlineSnapshot(`564`);
   });
 
   it('es-toolkit/compat', async () => {
     const bundleSize = await getBundleSize('es-toolkit/compat', 'mergeWith');
-    expect(bundleSize).toMatchInlineSnapshot(`5665`);
+    expect(bundleSize).toMatchInlineSnapshot(`6150`);
   });
 });

benchmarks/bundle-size/omit.spec.ts

@@ -14,6 +14,6 @@ describe('omit bundle size', () => {
 
   it('es-toolkit/compat', async () => {
     const bundleSize = await getBundleSize('es-toolkit/compat', 'omit');
-    expect(bundleSize).toMatchInlineSnapshot(`8042`);
+    expect(bundleSize).toMatchInlineSnapshot(`8227`);
   });
 });

benchmarks/bundle-size/throttle.spec.ts

@@ -9,7 +9,7 @@ describe('throttle bundle size', () => {
 
   it('es-toolkit', async () => {
     const bundleSize = await getBundleSize('es-toolkit', 'throttle');
-    expect(bundleSize).toMatchInlineSnapshot(`764`);
+    expect(bundleSize).toMatchInlineSnapshot(`855`);
   });
 
   it('es-toolkit/compat', async () => {

benchmarks/bundle-size/utils/getBundleSize.ts

@@ -1,7 +1,9 @@
 import esbuild from 'esbuild';
 import path from 'path';
 
-export async function getBundleSize(pkg: 'lodash-es' | 'es-toolkit' | 'es-toolkit/compat', funcName: string) {
+type Package = 'lodash-es' | 'es-toolkit' | 'es-toolkit/compat' | 'es-toolkit/iterator' | 'itertools' | '@fxts/core';
+
+export async function getBundleSize(pkg: Package, funcName: string) {
   const script = `import { ${funcName} } from "${pkg}"; console.log(${funcName})`;
 
   const bundled = await esbuild.build({

benchmarks/bundle-size/zipIterable.spec.ts

@@ -0,0 +1,19 @@
+import { describe, expect, it } from 'vitest';
+import { getBundleSize } from './utils/getBundleSize';
+
+describe('zipIterable bundle size', () => {
+  it('es-toolkit', async () => {
+    const bundleSize = await getBundleSize('es-toolkit/iterator', 'zipIterable');
+    expect(bundleSize).toMatchInlineSnapshot(`197`);
+  });
+
+  it('@fxts/core', async () => {
+    const bundleSize = await getBundleSize('@fxts/core', 'zip');
+    expect(bundleSize).toMatchInlineSnapshot(`6336`);
+  });
+
+  it('itertools', async () => {
+    const bundleSize = await getBundleSize('itertools', 'izip');
+    expect(bundleSize).toMatchInlineSnapshot(`337`);
+  });
+});

benchmarks/bundle-size/zipObjectDeep.spec.ts

@@ -9,6 +9,6 @@ describe('zipObjectDeep bundle size', () => {
 
   it('es-toolkit/compat', async () => {
     const bundleSize = await getBundleSize('es-toolkit/compat', 'zipObjectDeep');
-    expect(bundleSize).toMatchInlineSnapshot(`2297`);
+    expect(bundleSize).toMatchInlineSnapshot(`2935`);
   });
 });

benchmarks/bundle-size/zipWith.spec.ts

@@ -9,7 +9,7 @@ describe('zipWith bundle size', () => {
 
   it('es-toolkit', async () => {
     const bundleSize = await getBundleSize('es-toolkit', 'zipWith');
-    expect(bundleSize).toMatchInlineSnapshot(`198`);
+    expect(bundleSize).toMatchInlineSnapshot(`200`);
   });
 
   it('es-toolkit/compat', async () => {

benchmarks/package.json

@@ -12,8 +12,10 @@
     "vitest": "^4.0.17"
   },
   "devDependencies": {
+    "@fxts/core": "^1.26.0",
     "@types/lodash": "^4.17.20",
     "@types/lodash-es": "^4",
+    "itertools": "^2.6.0",
     "rfdc": "^1.4.1"
   }
 }

benchmarks/performance/chain.bench.ts

@@ -0,0 +1,58 @@
+import { bench, describe } from 'vitest';
+import { chain as chainEsToolkit_ } from 'es-toolkit/iterator';
+import { chain as chainItertools_ } from 'itertools';
+
+const chainEsToolkit = chainEsToolkit_;
+const chainItertools = chainItertools_;
+
+describe('chain', () => {
+  bench('es-toolkit/chain', () => {
+    const iter = chainEsToolkit([1, 2, 3], [4, 5, 6], [7, 8, 9]);
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+
+  bench('itertools/ichain', () => {
+    const iter = chainItertools([1, 2, 3], [4, 5, 6], [7, 8, 9]);
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+
+  bench('native spread', () => {
+    const iter = [
+      [1, 2, 3],
+      [4, 5, 6],
+      [7, 8, 9],
+    ].flat();
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+});
+
+describe('chain/largeArray', () => {
+  const largeArray = Array.from({ length: 10000 }, (_, i) => i);
+
+  bench('es-toolkit/chain', () => {
+    const iter = chainEsToolkit(largeArray, largeArray, largeArray);
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+
+  bench('itertools/ichain', () => {
+    const iter = chainItertools(largeArray, largeArray, largeArray);
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+
+  bench('native spread', () => {
+    const iter = [...largeArray, ...largeArray, ...largeArray];
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+});

benchmarks/performance/enumerate.bench.ts

@@ -0,0 +1,66 @@
+import { bench, describe } from 'vitest';
+import { enumerate as enumerateEsToolkit_ } from 'es-toolkit/iterator';
+import { zipWithIndex as zipWithIndexFxts_ } from '@fxts/core';
+
+const enumerateEsToolkit = enumerateEsToolkit_;
+const zipWithIndexFxts = zipWithIndexFxts_;
+
+describe('enumerate', () => {
+  bench('es-toolkit/enumerate', () => {
+    const iter = enumerateEsToolkit(['a', 'b', 'c']);
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+
+  bench('@fxts/core/zipWithIndex', () => {
+    const iter = zipWithIndexFxts(['a', 'b', 'c']);
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+
+  bench('Array.prototype.entries (native)', () => {
+    const arr = ['a', 'b', 'c'];
+    for (const _ of arr.entries()) {
+      /* consume */
+    }
+  });
+
+  bench('forEach with index (native)', () => {
+    const arr = ['a', 'b', 'c'];
+    arr.forEach((_, __) => {
+      /* consume */
+    });
+  });
+});
+
+describe('enumerate/largeArray', () => {
+  const largeArray = Array.from({ length: 10000 }, (_, i) => String(i));
+
+  bench('es-toolkit/enumerate', () => {
+    const iter = enumerateEsToolkit(largeArray);
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+
+  bench('@fxts/core/zipWithIndex', () => {
+    const iter = zipWithIndexFxts(largeArray);
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+
+  bench('Array.prototype.entries (native)', () => {
+    for (const _ of largeArray.entries()) {
+      /* consume */
+    }
+  });
+
+  bench('forEach with index (native)', () => {
+    largeArray.forEach((_, __) => {
+      /* consume */
+    });
+  });
+});

benchmarks/performance/zipIterable.bench.ts

@@ -0,0 +1,56 @@
+import { bench, describe } from 'vitest';
+import { zipIterable as zipIterableEsToolkit_ } from 'es-toolkit/iterator';
+import { izip as zipItertools_ } from 'itertools';
+import { zip as zipFxts_ } from '@fxts/core';
+
+const zipIterableEsToolkit = zipIterableEsToolkit_;
+const zipFxts = zipFxts_;
+const zipItertools = zipItertools_;
+
+describe('zipIterable', () => {
+  bench('es-toolkit/zipIterable', () => {
+    const iter = zipIterableEsToolkit([1, 2, 3], ['a', 'b', 'c']);
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+
+  bench('@fxts/core/zip', () => {
+    const iter = zipFxts([1, 2, 3], ['a', 'b', 'c']);
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+
+  bench('itertools/izip', () => {
+    const iter = zipItertools([1, 2, 3], ['a', 'b', 'c']);
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+});
+
+describe('zipIterable/largeArray', () => {
+  const largeArray = Array.from({ length: 10000 }, (_, i) => i);
+
+  bench('es-toolkit/zipIterable', () => {
+    const iter = zipIterableEsToolkit(largeArray, largeArray);
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+
+  bench('@fxts/core/zip', () => {
+    const iter = zipFxts(largeArray, largeArray);
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+
+  bench('itertools/izip', () => {
+    const iter = zipItertools(largeArray, largeArray);
+    for (const _ of iter) {
+      /* consume */
+    }
+  });
+});