jQuery callbacks.has()方法

jQuery中的callbacks.has()方法是用来回答列表中是否有任何回调附件。如果一个回调被作为一个参数传递，那么它回答它是否在列表中。

语法:

callbacks.has([callback])

参数:

callback。该参数定义了要搜索的回调，在列表中。

返回值：该方法要么返回真，要么返回假。

例子1：这个例子返回 “true”，因为’func’在列表中。

<!DOCTYPE HTML>
<html>
  
<head>
    <script src=
"https://code.jquery.com/jquery-3.5.0.js">
    </script>
</head>
  
<body style="text-align:center;">
    <h1 style="color:green;">
        GeeksForGeeks
    </h1>
  
    <p>
        JQuery | callbacks.has() method
    </p>
      
    <button onclick="Geeks();">
        click here
    </button>
      
    <p id="GFG"></p>
  
    <script>
        var el_down = document.getElementById("GFG");
        var res = "";
        var callbacks = jQuery.Callbacks();
          
        function Geeks() {
            var func = function (val) {
                res = res + "value passed is - " + val;
            };
            callbacks.add(func); // function added to list
            callbacks.fire("gfg_1");
            el_down.innerHTML = callbacks.has();
        } 
    </script>
</body>
  
</html>

输出:
jQuery callbacks.has()方法

例子2：这个例子返回 “false”，因为’func2’不在列表中。

<!DOCTYPE HTML>
<html>
  
<head>
    <script src=
"https://code.jquery.com/jquery-3.5.0.js">
    </script>
</head>
  
<body style="text-align:center;">
    <h1 style="color:green;">
        GeeksForGeeks
    </h1>
  
    <p>
        JQuery | callbacks.has() method
    </p>
      
    <button onclick="Geeks();">
        click here
    </button>
      
    <p id="GFG_DOWN"></p>
  
    <script>
        var el_down = document.getElementById("GFG_DOWN");
        var res = "";
        var callbacks = jQuery.Callbacks();
  
        function Geeks() {
            var func1 = function (val) {
                res = res + "value passed is - " + val;
            };
            var func2 = function (val) {
                res = res + "value passed is - " + val;
            };
  
            // Function added to list
            callbacks.add(func1); 
            callbacks.fire("gfg_1");
            el_down.innerHTML = callbacks.has(func2);
        } 
    </script>
</body>
  
</html>

输出:
jQuery callbacks.has()方法