I would use the underscore.js or lodash source code to find a well tested version of this function.
Here is the slightly modified version of the underscore code to remove all references to underscore.js itself:
// Returns a function, that, when invoked, will only be triggered at most once // during a given window of time. Normally, the throttled function will run // as much as it can, without ever going more than once per `wait` duration; // but if you'd like to disable the execution on the leading edge, pass // `{leading: false}`. To disable execution on the trailing edge, ditto. function throttle(func, wait, options) { var context, args, result; var timeout = null; var previous = 0; if (!options) options = {}; var later = function() { previous = options.leading === false ? 0 : Date.now(); timeout = null; result = func.apply(context, args); if (!timeout) context = args = null; }; return function() { var now = Date.now(); if (!previous && options.leading === false) previous = now; var remaining = wait - (now - previous); context = this; args = arguments; if (remaining <= 0 || remaining > wait) { if (timeout) { clearTimeout(timeout); timeout = null; } previous = now; result = func.apply(context, args); if (!timeout) context = args = null; } else if (!timeout && options.trailing !== false) { timeout = setTimeout(later, remaining); } return result; }; };
Please note that this code can be simplified if you don’t need all the options that underscore support.
Please find below a very simple and non-configurable version of this function:
function throttle (callback, limit) { var waiting = false; // Initially, we're not waiting return function () { // We return a throttled function if (!waiting) { // If we're not waiting callback.apply(this, arguments); // Execute users function waiting = true; // Prevent future invocations setTimeout(function () { // After a period of time waiting = false; // And allow future invocations }, limit); } } }
Edit 1: Removed another reference to underscore, thx to @Zettam ‘s comment
Edit 2: Added suggestion about lodash and possible code simplification, thx to @lolzery @wowzery ‘s comment
Edit 3: Due to popular requests, I added a very simple, non-configurable version of the function, adapted from @vsync ‘s comment