callbacks.has()

类别：回调函数对象

callbacks.has( [callback ] )返回类型：Boolean

描述：确定一个列表是否附加了回调函数。如果提供了一个回调函数作为参数，确定它是否在列表中。

示例：

使用callbacks.has()来检查某个回调函数列表是否包含了一个特定的回调函数：

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// 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