How to use callback function in js

A callback function in JavaScript is a function that is called after another function has completed execution to perform additional operations. Its usage steps include: defining a callback function containing the code to be executed. Pass the callback function to the main function as a parameter. After the main function performs a specific task, the callback function is called.

Callback function in JavaScript

What is a callback function?

The callback function is a function that is called after the execution of another function (the main function) is completed. Its function is to allow the main function to perform additional operations after performing a specific task.

Usage of callback function

The steps to use callback function are as follows:

1. Define callback function: Define a A function that contains code to be executed after the main function completes execution.
2. Pass the callback function to the main function: When calling the main function, pass the callback function as a parameter.
3. Execute the callback function in the main function: When the main function has finished performing its specific task, it calls the passed callback function.

Example

The following example shows how to use callback functions in JavaScript:

<code class="js">function printMessage(message) {
  console.log(message);
}

function delayPrint(message, delay) {
  setTimeout(() => {
    printMessage(message);
  }, delay);
}

delayPrint("Hello World!", 2000);</code>

In this example:

• printMessage is a callback function used to print messages.
• delayPrint is a main function that calls setTimeout to delay the execution of printMessage.
• When delayPrint completes its task (after 2 seconds), it calls the callback function printMessage.

Advantages

The advantages of using callback functions include:

• Asynchronous programming: Callback functions use Asynchronous programming made easy, where operations can be performed outside the event loop thread.
• Extensibility: Callback functions allow you to add or remove additional functionality without modifying the main function.
• Code reuse: Callback functions can be reused by multiple functions, thereby improving code reusability.

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