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How to call a function that return another function in JavaScript ?

  • Last Updated : 24 Jul, 2019
Geek Week

The task is to call a function which returns another function with the help of JavaScript. we’re going to discuss few techniques.

Approach:

  • First call the first function-1.
  • Define a function-2 inside the function-1.
  • Return the call to the function-2 from the function-1.

Example 1: In this example, “from function 2” is returned from the fun2 which is finally returned by fun1.




<!DOCTYPE HTML>
<html>
  
<head>
    <title>
        JavaScript 
      | Function that return a function.
    </title>
</head>
  
<body style="text-align:center;"
      id="body">
    <h1 style="color:green;">  
            GeeksForGeeks
        </h1>
    <p id="GFG_UP" 
       style="font-size: 19px;
              font-weight: bold;">
    </p>
    <button onclick="GFG_Fun()">
        click here
    </button>
    <p id="GFG_DOWN"
       style="color: green; 
              font-size: 24px;
              font-weight: bold;">
    </p>
    <script>
        var el_up = document.getElementById("GFG_UP");
        var el_down = document.getElementById("GFG_DOWN");
        el_up.innerHTML = 
          "Click on the button to call a function, "+
          "which returns the call to another function.";
  
        function fun1() {
            function fun2() {
                return "From function fun2";
            }
            return fun2();
        }
  
        function GFG_Fun() {
            el_down.innerHTML = fun1();
        }
    </script>
</body>
  
</html>

Output:

  • Before clicking on the button:
  • After clicking on the button:

Example 2: In this example, “Alert from fun2” is returned from the fun2 alongwith an alert, Returned value finally returned by fun1.




<!DOCTYPE HTML>
<html>
  
<head>
    <title>
        JavaScript 
      | Function that return a function.
    </title>
</head>
  
<body style="text-align:center;"
      id="body">
    <h1 style="color:green;">  
            GeeksForGeeks
        </h1>
    <p id="GFG_UP"
       style="font-size: 19px;
              font-weight: bold;">
    </p>
    <button onclick="GFG_Fun()">
        click here
    </button>
    <p id="GFG_DOWN" 
       style="color: green; 
              font-size: 24px; 
              font-weight: bold;">
    </p>
    <script>
        var el_up = document.getElementById("GFG_UP");
        var el_down = document.getElementById("GFG_DOWN");
        el_up.innerHTML = 
          "Click on the button to call a function, "+
          "which returns the call to another function.";
  
        function fun1() {
            function fun2() {
                alert("From function fun2");
                return "Alert from fun2 ";
            }
            return fun2();
        }
  
        function GFG_Fun() {
            el_down.innerHTML = fun1();
        }
    </script>
</body>
  
</html>

Output:

  • Before clicking on the button:
  • After clicking on the button:

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