### 返回值:Booleancallbacks.has(callback) ### 概述 确定是否提供的回调列表 ### 参数 #### **callback***V1.7* 用来搜索的回调。 ### 示例 #### 描述: 用 callbacks.has() 检查是否回调列表中包含一个特定的回调: ##### jQuery 代码: ~~~ // a sample logging function to be added to a callbacks list var foo = function( value1, value2 ){ console.log( 'Received:' + value1 + ',' + value2 ); } // a second function which will not be added to the list var bar = function( value1, value2 ){ console.log( 'foobar'); } var callbacks = $.Callbacks(); // add the log method to the callbacks list callbacks.add( foo ); // determine which callbacks are in the list console.log( callbacks.has( foo ) ); // true console.log( callbacks.has( bar ) ); // false ~~~