DelayedTask.js

/**
 * @class Ext.util.DelayedTask
 * Provides a convenient method of performing setTimeout where a new
 * timeout cancels the old timeout. 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.
 * @constructor The parameters to this constructor serve as defaults and are not required.
 * @param {Function} fn （可选） The default function to timeout
 * @param {Object} scope （可选） The default scope of that timeout
 * @param {Array} args （可选） The default Array of arguments
 */
Ext.util.DelayedTask = function(fn, scope, args){
    var id = null, d, t;

    var call = function(){
        var now = new Date().getTime();
        if(now - t >= d){
            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 （可选） Overrides function passed to constructor
     * @param {Object} newScope （可选） Overrides scope passed to constructor
     * @param {Array} newArgs （可选） Overrides args passed to constructor
     */
    this.delay = function(delay, newFn, newScope, newArgs){
        if(id && delay != d){
            this.cancel();
        }
        d = delay;
        t = new Date().getTime();
        fn = newFn || fn;
        scope = newScope || scope;
        args = newArgs || args;
        if(!id){
            id = setInterval(call, d);
        }
    };

    /**
     * Cancel the last queued timeout
     */
    this.cancel = function(){
        if(id){
            clearInterval(id);
            id = null;
        }
    };
};