/** * @class Ext.util.DelayedTask *

The DelayedTask class provides a convenient way to "buffer" the execution of a method, * performing setTimeout where a new timeout cancels the old timeout. When called, the * task will wait the specified time period before executing. If durng that time period, * the task is called again, the original call will be cancelled. This continues so that * the function is only called a single time for each iteration.

*

This method is especially useful for things like detecting whether a user has finished * typing in a text field. An example would be performing validation on a keypress. You can * use this class to buffer the keypress events for a certain number of milliseconds, and * perform only if they stop for that amount of time. Usage:


var task = new Ext.util.DelayedTask(function(){
    alert(Ext.getDom('myInputField').value.length);
});
// Wait 500ms before calling our function. If the user presses another key 
// during that 500ms, it will be cancelled and we'll wait another 500ms.
Ext.get('myInputField').on('keypress', function(){
    task.{@link #delay}(500); 
});
 * 
*

Note that we are using a DelayedTask here to illustrate a point. The configuration * option buffer for {@link Ext.util.Observable#addListener addListener/on} will * also setup a delayed task for you to buffer events.

* @constructor The parameters to this constructor serve as defaults and are not required. * @param {Function} fn (optional) The default function to timeout * @param {Object} scope (optional) The default scope of that timeout * @param {Array} args (optional) The default Array of arguments */ Ext.util.DelayedTask = function(fn, scope, args){ var me = this, id, call = function(){ clearInterval(id); id = null; fn.apply(scope, args || []); };
/** * Cancels any pending timeout and queues a new one * @param {Number} delay The milliseconds to delay * @param {Function} newFn (optional) Overrides function passed to constructor * @param {Object} newScope (optional) Overrides scope passed to constructor * @param {Array} newArgs (optional) Overrides args passed to constructor */ me.delay = function(delay, newFn, newScope, newArgs){ me.cancel(); fn = newFn || fn; scope = newScope || scope; args = newArgs || args; id = setInterval(call, delay); };
/** * Cancel the last queued timeout */ me.cancel = function(){ if(id){ clearInterval(id); id = null; } }; };