JavaScript | Function Invocation

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:

My Personal Notes

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