How to Create Callback Function With Parameters in JavaScript

In JavaScript, when we pass a function to another function as a parameter, it is called a callback function.

The function takes another function as a parameter and calls it inside.

A callback function makes sure that a function will not run until the task completes.

Create a Callback Function by Passing a Function as a Parameters in JavaScript

We will create a callback function by passing the function as a parameter to another function. We call the function back right after the task completes.

We will make a function named sayName. Then we create a callback function named sayHowAreYou.

We want to pass another parameter in the callback function by the formal argument n.

function sayName(name, cb) {
  console.log(`Hello  ${name}`);
  cb(name);
}
function sayHowAreYou(n) {
  console.log('How are you? ' + n);
}
sayName('DelftStack', sayHowAreYou);

Output:

Hello  DelftStack
How are you? DelftStack

When we call the first function, it will return Hello DelftStack. Then we greeted how are you, so we called the callback function for that purpose.

When we had passed the callback function parameter, it returned Hello DelftStack, How are you? DelftStack.