niksy/throttle-debounce

Throttle and debounce functions.

throttle-debounce

Throttle and debounce functions.

This module is the same as jquery-throttle-debounce (with some differences), but it’s transferred to ES Modules and CommonJS format.

Install

npm install throttle-debounce --save

Usage

throttle

import { throttle } from 'throttle-debounce';

const throttleFunc = throttle(
	1000,
	(num) => {
		console.log('num:', num);
	},
	{ noLeading: false, noTrailing: false }
);

// Can also be used like this, because noLeading and noTrailing are false by default
const throttleFunc = throttle(1000, (num) => {
	console.log('num:', num);
});

throttleFunc(1); // Will execute the callback
throttleFunc(2); // Won’t execute callback
throttleFunc(3); // Won’t execute callback

// Will execute the callback, because noTrailing is false,
// but if we set noTrailing to true, this callback won’t be executed
throttleFunc(4);

setTimeout(() => {
	throttleFunc(10); // Will execute the callback
}, 1200);

// Output
// num: 1
// num: 4
// num: 10

debounce

import { debounce } from 'throttle-debounce';

const debounceFunc = debounce(
	1000,
	(num) => {
		console.log('num:', num);
	},
	{ atBegin: false }
);

// Can also be used like this, because atBegin is false by default
const debounceFunc = debounce(1000, (num) => {
	console.log('num:', num);
});

// Won’t execute the callback, because atBegin is false,
// but if we set atBegin to true, this callback will be executed.
debounceFunc(1);

debounceFunc(2); // Won’t execute callback
debounceFunc(3); // Won’t execute callback

// Will execute the callback,
// but if we set atBegin to true, this callback won’t be executed.
debounceFunc(4);

setTimeout(() => {
	debounceFunc(10); // Will execute the callback
}, 1200);

// Output
// num: 4
// num: 10

Cancelling

Debounce and throttle can both be cancelled by calling the cancel function.

const throttleFunc = throttle(300, () => {
	// Throttled function
});

throttleFunc.cancel();

const debounceFunc = debounce(300, () => {
	// Debounced function
});

debounceFunc.cancel();

The logic that is being throttled or debounced will no longer be called.

To cancel only one upcoming debounced call, you can pass upcomingOnly: true option to cancel function:

const debounceFunc = debounce(300, () => {
	// Debounced function
});

debounceFunc(); // will not be invoked

debounceFunc.cancel({ upcomingOnly: true });

debounceFunc(); // will be invoked

API

throttle(delay, callback, { noLeading, noTrailing, debounceMode })

Returns: Function

Throttle execution of a function. Especially useful for rate limiting execution of handlers on events like resize and scroll.

delay

Type: Number

A zero-or-greater delay in milliseconds. For event callbacks, values around 100 or 250 (or even higher) are most useful.

callback

Type: Function

A function to be executed after delay milliseconds. The this context and all arguments are passed through, as-is, to callback when the throttled-function is executed.

noTrailing

Type: Boolean

Optional, defaults to false. If noTrailing is true, callback will only execute every delay milliseconds while the throttled-function is being called. If noTrailing is false or unspecified, callback will be executed one final time after the last throttled-function call. (After the throttled-function has not been called for delay milliseconds, the internal counter is reset)

noLeading

Type: Boolean

Optional, defaults to false. If noLeading is false, the first throttled-function call will execute callback immediately. If noLeading is true, the first the callback execution will be skipped. It should be noted that callback will never executed if both noLeading = true and noTrailing = true.

debounceMode

Type: Boolean

If debounceMode is true (at begin), schedule clear to execute after delay ms. If debounceMode is false (at end), schedule callback to execute after delay ms.

debounce(delay, callback, { atBegin })

Returns: Function

Debounce execution of a function. Debouncing, unlike throttling, guarantees that a function is only executed a single time, either at the very beginning of a series of calls, or at the very end.

delay

Type: Number

A zero-or-greater delay in milliseconds. For event callbacks, values around 100 or 250 (or even higher) are most useful.

callback

Type: Function

A function to be executed after delay milliseconds. The this context and all arguments are passed through, as-is, to callback when the debounced-function is executed.

atBegin

Type: Boolean

Optional, defaults to false. If atBegin is false or unspecified, callback will only be executed delay milliseconds after the last debounced-function call. If atBegin is true, callback will be executed only at the first debounced-function call. (After the throttled-function has not been called for delay milliseconds, the internal counter is reset).

Differences with original module

• Dependancy on jQuery is removed, so if you rely on GUIDs set by jQuery, plan accordingly
• There is no standalone version available, so don’t rely on $.throttle and $.debounce to be available

Browser support

Tested in Chrome 72, Edge 15, Firefox 65 and should work in all modern browsers (support based on Browserslist configuration).

Test

For automated tests, run npm run test:automated (append :watch for watcher support).

License

MIT © Ivan Nikolić