JavaScript Passing parameters to a callback function

Passing a function as a parameter in JavaScript

Last Updated : 13 Jun, 2023

In this article, we will pass a function as a parameter in JavaScript. Passing a function as an argument to the function is quite similar to passing a variable as an argument to the function. So variables can be returned from a function.

The below examples describe passing a function as a parameter to another function.

Example 1: This example passes a function geeks_inner to the function geeks_outer as an argument.

Javascript

Javascript

function geeks_inner(value){
    return 'hello User!';
}
function geeks_outer(func){
    console.log(geeks_inner());
}
 
geeks_outer(geeks_inner);

Output

hello User!

Example 2: This example passes a function geeks_inner along with an argument ‘Geeks!’ to the function geeks_outer as an argument.

Javascript

Javascript

function geeks_inner(value) {
    return 'hello ' + value;
}
function geeks_outer(a, func) {
    console.log(func(a));
}
 
geeks_outer('Geeks!', geeks_inner);

Output

hello Geeks!

Example 3: Here in this example, a smaller function is passed as an argument in the sayHello function. So here we are passing a smaller function address to the function sayHello.

Javascript

Javascript

function sayHello(param) {
    console.log("hello", param);
    param();
    return "Hiii Geeks for Geeks"
}
 
// Function address
function smaller() {
    console.log("Is everything alright")
}
 
// Function call
const returnHello = sayHello(smaller)
console.log(returnHello)

Output

hello [Function: smaller]
Is everything alright
Hiii Geeks for Geeks

JavaScript Passing parameters to a callback function

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