@gravityforms/utils/src/data/delay.js

JavaScript utilities for Gravity Forms development.

/* eslint-disable */
/**
 * @module delay
 * @description A chainable function for delaying execution of a function or group of functions.
 *
 * @since 1.0.0
 *
 * @param {Function} fn Function to execute.
 * @param {number}   t  Delay time in milliseconds.
 *
 * @return {Function} Returns the a function that can then be chained with another call.
 *
 * @example
 * import { delay } from "@gravityforms/utils";
 *
 * function Example() {
 *   delay(fn1, 400).delay(fn2, 500);
 * }
 *
 * function fn1() {
 * 	console.log( 'fn1: ' + Date.now() );
 * }
 * function fn2() {
 * 	console.log( 'fn2: ' + Date.now() );
 * }
 *
 */
export default function( fn = () => {}, t = 100 ) {
	let queue = [];
	let self;
	let timer;

	/**
	 *
	 * @param  fn
	 * @param  t
	 */
	function schedule( fn, t ) {
		timer = window.setTimeout( function() {
			timer = null;
			fn();
			if ( queue.length ) {
				const item = queue.shift();
				schedule( item.fn, item.t );
			}
		}, t );
	}

	self = {
		delay( fn, t ) {
			// if already queuing things or running a timer,
			//   then just add to the queue
			if ( queue.length || timer ) {
				queue.push( { fn, t } );
			} else {
				// no queue or timer yet, so schedule the timer
				schedule( fn, t );
			}
			return self;
		},
		cancel() {
			window.clearTimeout( timer );
			queue = [];
			return self;
		},
	};
	return self.delay( fn, t );
}