Explain invoking function in JavaScript

In this article, we will learn about invoking the function in Javascript, along with understanding its implementation through examples. Function Invoking is a process to execute the code inside the function when some argument is passed to invoke it. You can invoke a function multiple times by declaring the function only once. When the function is defined, the code inside a function will not be executed. It is common to use the term “call a function” instead of “invoke a function”. Although, there has a difference between these two terms. When you make a function call, you are directly telling the function to execute, whereas when you invoke a function, you are letting something execute the function. For instance,

functionName();

Here, we have invoked the function ie., letting it run, by calling the function directly.

Syntax:

function myFunction( var ) {
   return var;
}
myFunction( value );

Here, by calling myFunction, you are invoking value, which is being called indirectly.

Invoking a Function as a Method: We can define the function as an object method.

Syntax:

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.

We will understand the above concepts through examples.

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

HTML

<h2 style="color:green">GeeksforGeeks</h2>
<p> Function returns the addition of 10 and 15 </p>

<p id="geeks"></p>

<script>
    function add(n1, n2) {
        return(n1 + n2);
    }
    document.getElementById("geeks").innerHTML =
    window.add(10, 15);
</script>

Output:

Example 2: This example illustrates this keyword to point to the current object.

Javascript

const obj={
    first_name:"Steve",
    last_name:"smith",
    name:function(){
        console.log(`Full name : ${this.first_name} ${this.last_name}`);
    }
};
obj.name();

Output:

Full name : Steve smith