Async JavaScript.txt

In its simplest form, JS is synchronous, blocking and single-threaded.
But JS can execute asynchronously without blocking UI with the help of functions and API's provided by Web Browsers.

Timers & Intervals
Timers are used to execute code once after a specified period of time.
Intervals are used to execute code over and over again at regular intervals.
They are not part of JS, but are the functionalities implemented by browser and used by JS with the name of setTimeout and setInterval.
Syntax: setTimeout(function OR reference to function to be executed, timer in milliseconds, param1, param2, ...)
Syntax: setInterval(function OR reference to function to be executed, interval in milliseconds, param1, param2, ...)
Timer & Interval is the minimum delay, not guaranteed, before executing the function. Call Stack needs to be empty after the delay to execute the function.
Both functions return identifier for themselves which can be used to clear it by passing identifier to clearTimeout & clearInterval.
Immediately(OR before executing,) clearing timeouts & intervals stop them from executing at once.

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