/*! * jQuery throttle / debounce - v1.1 - 3/7/2010 * http://benalman.com/projects/jquery-throttle-debounce-plugin/ * * Copyright (c) 2010 "Cowboy" Ben Alman * Dual licensed under the MIT and GPL licenses. * http://benalman.com/about/license/ */ // Script: jQuery throttle / debounce: Sometimes, less is more! // // *Version: 1.1, Last updated: 3/7/2010* // // Project Home - http://benalman.com/projects/jquery-throttle-debounce-plugin/ // GitHub - http://github.com/cowboy/jquery-throttle-debounce/ // Source - http://github.com/cowboy/jquery-throttle-debounce/raw/master/jquery.ba-throttle-debounce.js // (Minified) - http://github.com/cowboy/jquery-throttle-debounce/raw/master/jquery.ba-throttle-debounce.min.js (0.7kb) // // About: License // // Copyright (c) 2010 "Cowboy" Ben Alman, // Dual licensed under the MIT and GPL licenses. // http://benalman.com/about/license/ // // About: Examples // // These working examples, complete with fully commented code, illustrate a few // ways in which this plugin can be used. // // Throttle - http://benalman.com/code/projects/jquery-throttle-debounce/examples/throttle/ // Debounce - http://benalman.com/code/projects/jquery-throttle-debounce/examples/debounce/ // // About: Support and Testing // // Information about what version or versions of jQuery this plugin has been // tested with, what browsers it has been tested in, and where the unit tests // reside (so you can test it yourself). // // jQuery Versions - none, 1.3.2, 1.4.2 // Browsers Tested - Internet Explorer 6-8, Firefox 2-3.6, Safari 3-4, Chrome 4-5, Opera 9.6-10.1. // Unit Tests - http://benalman.com/code/projects/jquery-throttle-debounce/unit/ // // About: Release History // // 1.1 - (3/7/2010) Fixed a bug in <jQuery.throttle> where trailing callbacks // executed later than they should. Reworked a fair amount of internal // logic as well. // 1.0 - (3/6/2010) Initial release as a stand-alone project. Migrated over // from jquery-misc repo v0.4 to jquery-throttle repo v1.0, added the // no_trailing throttle parameter and debounce functionality. // // Topic: Note for non-jQuery users // // jQuery isn't actually required for this plugin, because nothing internal // uses any jQuery methods or properties. jQuery is just used as a namespace // under which these methods can exist. // // Since jQuery isn't actually required for this plugin, if jQuery doesn't exist // when this plugin is loaded, the method described below will be created in // the `Cowboy` namespace. Usage will be exactly the same, but instead of // $.method() or jQuery.method(), you'll need to use Cowboy.method(). (function(window,undefined){ '$:nomunge'; // Used by YUI compressor. // Since jQuery really isn't required for this plugin, use `jQuery` as the // namespace only if it already exists, otherwise use the `Cowboy` namespace, // creating it if necessary. var $ = window.jQuery || window.Cowboy || ( window.Cowboy = {} ), // Internal method reference. jq_throttle; // Method: jQuery.throttle // // Throttle execution of a function. Especially useful for rate limiting // execution of handlers on events like resize and scroll. If you want to // rate-limit execution of a function to a single time, see the // <jQuery.debounce> method. // // In this visualization, | is a throttled-function call and X is the actual // callback execution: // // > Throttled with `no_trailing` specified as false or unspecified: // > ||||||||||||||||||||||||| (pause) ||||||||||||||||||||||||| // > X X X X X X X X X X X X // > // > Throttled with `no_trailing` specified as true: // > ||||||||||||||||||||||||| (pause) ||||||||||||||||||||||||| // > X X X X X X X X X X // // Usage: // // > var throttled = jQuery.throttle( delay, [ no_trailing, ] callback ); // > // > jQuery('selector').bind( 'someevent', throttled ); // > jQuery('selector').unbind( 'someevent', throttled ); // // This also works in jQuery 1.4+: // // > jQuery('selector').bind( 'someevent', jQuery.throttle( delay, [ no_trailing, ] callback ) ); // > jQuery('selector').unbind( 'someevent', callback ); // // Arguments: // // delay - (Number) A zero-or-greater delay in milliseconds. For event // callbacks, values around 100 or 250 (or even higher) are most useful. // no_trailing - (Boolean) Optional, defaults to false. If no_trailing is // true, callback will only execute every `delay` milliseconds while the // throttled-function is being called. If no_trailing 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) // callback - (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. // // Returns: // // (Function) A new, throttled, function. $.throttle = jq_throttle = function( delay, no_trailing, callback, debounce_mode ) { // After wrapper has stopped being called, this timeout ensures that // `callback` is executed at the proper times in `throttle` and `end` // debounce modes. var timeout_id, // Keep track of the last time `callback` was executed. last_exec = 0; // `no_trailing` defaults to falsy. if ( typeof no_trailing !== 'boolean' ) { debounce_mode = callback; callback = no_trailing; no_trailing = undefined; } // The `wrapper` function encapsulates all of the throttling / debouncing // functionality and when executed will limit the rate at which `callback` // is executed. function wrapper() { var that = this, elapsed = +new Date() - last_exec, args = arguments; // Execute `callback` and update the `last_exec` timestamp. function exec() { last_exec = +new Date(); callback.apply( that, args ); }; // If `debounce_mode` is true (at_begin) this is used to clear the flag // to allow future `callback` executions. function clear() { timeout_id = undefined; }; if ( debounce_mode && !timeout_id ) { // Since `wrapper` is being called for the first time and // `debounce_mode` is true (at_begin), execute `callback`. exec(); } // Clear any existing timeout. timeout_id && clearTimeout( timeout_id ); if ( debounce_mode === undefined && elapsed > delay ) { // In throttle mode, if `delay` time has been exceeded, execute // `callback`. exec(); } else if ( no_trailing !== true ) { // In trailing throttle mode, since `delay` time has not been // exceeded, schedule `callback` to execute `delay` ms after most // recent execution. // // If `debounce_mode` is true (at_begin), schedule `clear` to execute // after `delay` ms. // // If `debounce_mode` is false (at end), schedule `callback` to // execute after `delay` ms. timeout_id = setTimeout( debounce_mode ? clear : exec, debounce_mode === undefined ? delay - elapsed : delay ); } }; // Set the guid of `wrapper` function to the same of original callback, so // it can be removed in jQuery 1.4+ .unbind or .die by using the original // callback as a reference. if ( $.guid ) { wrapper.guid = callback.guid = callback.guid || $.guid++; } // Return the wrapper function. return wrapper; }; // Method: jQuery.debounce // // 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. If you want to // simply rate-limit execution of a function, see the <jQuery.throttle> // method. // // In this visualization, | is a debounced-function call and X is the actual // callback execution: // // > Debounced with `at_begin` specified as false or unspecified: // > ||||||||||||||||||||||||| (pause) ||||||||||||||||||||||||| // > X X // > // > Debounced with `at_begin` specified as true: // > ||||||||||||||||||||||||| (pause) ||||||||||||||||||||||||| // > X X // // Usage: // // > var debounced = jQuery.debounce( delay, [ at_begin, ] callback ); // > // > jQuery('selector').bind( 'someevent', debounced ); // > jQuery('selector').unbind( 'someevent', debounced ); // // This also works in jQuery 1.4+: // // > jQuery('selector').bind( 'someevent', jQuery.debounce( delay, [ at_begin, ] callback ) ); // > jQuery('selector').unbind( 'someevent', callback ); // // Arguments: // // delay - (Number) A zero-or-greater delay in milliseconds. For event // callbacks, values around 100 or 250 (or even higher) are most useful. // at_begin - (Boolean) Optional, defaults to false. If at_begin is false or // unspecified, callback will only be executed `delay` milliseconds after // the last debounced-function call. If at_begin 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) // callback - (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. // // Returns: // // (Function) A new, debounced, function. $.debounce = function( delay, at_begin, callback ) { return callback === undefined ? jq_throttle( delay, at_begin, false ) : jq_throttle( delay, callback, at_begin !== false ); }; })(this);