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jquery.ba-throttle-debounce.js
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jquery.ba-throttle-debounce.js 10.01 KiB
/*!
* 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);