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jQuery callbacks.add() Method
  • Last Updated : 07 Jul, 2020

The jQuery callbacks.add() method is used to add a callback or a collection of callbacks to a callback list. This method returns the callback object onto which it is attached (this).

Syntax:

callbacks.add(callbacks)

Parameters:

  • callbacks: This parameter holds a function, or an array of functions, that are to be added to the callback list.

Example 1: This method adds a method fun1() to the callback and call it.




<!DOCTYPE HTML>
<html>
  
<head>
    <title>
        jQuery callbacks.add() method
    </title>
  
    <script src=
    </script>
</head>
  
<body style="text-align:center;">
    <h1 style="color:green;">
        GeeksForGeeks
    </h1>
      
    <p id="GFG_UP"></p>
      
    <button onclick="Geeks();">
        click here
    </button>
      
    <p id="GFG_DOWN"></p>
      
    <script>
        var el_up = document.getElementById("GFG_UP");
        var el_down = document.getElementById("GFG_DOWN");
        el_up.innerHTML = 
                    "JQuery | callbacks.add() method";
        var res = "";
          
        function Geeks() {
  
            // First function to be added to the list
            var fun1 = function (val) {
                res = res + "This is function 1 and"
                + " value passed is " + val + "<br>";
            };
            var callbacks = jQuery.Callbacks();
            callbacks.add(fun1); //Aadding the func1
            callbacks.fire("GFG_1"); // Calling the fun1
            el_down.innerHTML = res;
        
    </script>
</body>
  
</html>

Output:

Example 2: This example adds method fun1() and fun2() to the callbacks and then calls them. Notice that at second time the fire() method is called, it calls both the functions with the same argument ‘GFG_2’.




<!DOCTYPE HTML>
<html>
  
<head>
    <title>
        jQuery callbacks.add() method
    </title>
      
    <script src=
    </script>
</head>
  
<body style="text-align:center;">
    <h1 style="color:green;">
        GeeksForGeeks
    </h1>
      
    <p id="GFG_UP"></p>
      
    <button onclick="Geeks();">
        click here
    </button>
      
    <p id="GFG_DOWN"></p>
      
    <script>
        var el_up = document.getElementById("GFG_UP");
        var el_down = document.getElementById("GFG_DOWN");
        el_up.innerHTML = 
                "JQuery | callbacks.add() method";
        var res = "";
  
        function Geeks() {
  
            // First function to be added to the list
            var fun1 = function (val) {
                res = res + "This is function 1 and"
                + " value passed is " + val + "<br>";
            };
  
            // Second function to  be added to the list
            var fun2 = function (val) {
                res = res + "This is function 2 and "
                    + "value passed is" + val + "<br>";
            };
  
            var callbacks = jQuery.Callbacks();
  
            // Adding the function 1
            callbacks.add(fun1);
  
            // Calling the function 1
            callbacks.fire("GFG_1");
  
            // Adding the function 2
            callbacks.add(fun2); 
  
            // Calling the function 2
            callbacks.fire("GFG_2"); 
  
            // res of the both functions
            el_down.innerHTML = res; 
        
    </script>
</body>
  
</html

Output:




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