JavaScript Function Invocation

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The JavaScript Function Invocation is used to execute 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:

let myObject = {
    let : value,
    functionName: function () {
        return this.let;
    }
}
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 uses function invocation to add two numbers.

html

<!DOCTYPE html>
<html lang="en">
<head>
    <title>JavaScript Function Invocation</title>
</head>
 
<body style="text-align:center;">
    <h2 style="color:green">GeeksForGeeks</h2>
    <h4>JavaScript Function Invocation</h4>
    <p>
        Function returns the addition
        of 50 and 60
    </p>
    <p id="zambiatek"></p>
 
    <!-- Script to add two numbers -->
    <script>
        function myFunction(a, b) {
            return a + b;
        }
 
        document.getElementById("zambiatek").innerHTML
            = window.myFunction(50, 60);
    </script>
</body>
</html>

Output:

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

Javascript

let myObject = {
    firstName: "Geeks",
    middleName: "for",
    lastName: "Geeks",
    fullName: function () {
        return this.firstName + this.middleName
            + this.lastName;
    }
}
console.log(myObject.fullName());