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JavaScript | Function Invocation
  • Last Updated : 07 Mar, 2019

JavaScript Function Invocation is used to executes the function code and it is common to use the term “call a function” instead of “invoke a function”. The code inside a function is executed when the function is invoked.

Syntax:

  • Invoking a Function as a Function:
    function myFunction( var ) {
        return var;
    }
    myFunction( value );
  • Invoking a Function as a Method:
    var myObject = {
        var : value,
        functionName: function () {
            return this.var;
        }
    }
    myObject.functionName();  

Parameters: It contains two parameters as mentioned above and described below:

  • functionName: The functionName method is a function and this function belongs to the object and myObject is the owner of the function.
  • this: The parameter this is the object that owns the JavaScript code and in this case the value of this is myObject.

Example 1: This example use function invocation to add two numbers.




<!DOCTYPE html>
<html>
  
<head>
    <title>
        JavaScript Function Invocation
    </title>
</head>
  
<body style="text-align:center;">
      
    <h2>GeeksForGeeks</h2>
          
    <p>
        Function returns the addition
        of 50 and 60
    </p>
          
    <p id="geeks"></p>
      
    <!-- Script to add two numbers -->
    <script>
        function myFunction(a, b) {
            return a + b;
        }
              
        document.getElementById("geeks").innerHTML
                = window.myFunction(50, 60); 
    </script>
</body>
  
</html>                    

Output:

Example 2: This example use function invocation to concatenate strings.




<!DOCTYPE html>
<html>
  
<head>
    <title>
        JavaScript Function Invocation
    </title>
</head>
  
<body style="text-align:center;">
      
    <h2>GeeksForGeeks</h2>
      
    <p>
        myObject.fullName() will return
        GeeksforGeeks
    </p>
      
    <p id="geeks"></p>
      
    <!-- Script to implement Function Invocation -->
    <script>
        var myObject = {
            firstName:"Geeks",
            middleName:"for",
            lastName: "Geeks",
            fullName: function() {
                return this.firstName + this.middleName
                        + this.lastName;
            }
        }
        document.getElementById("geeks").innerHTML
                = myObject.fullName(); 
    </script>
</body>
  
</html>                    

Output:




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