Coding with JavaScript For Dummies

Chapter 15

Understanding Callbacks and Closures

In This Chapter

Understanding callback functions

Using callbacks

Creating closures

“O, call back yesterday, bid time return.”

— William Shakespeare

Callbacks and closures are two of the most useful and widely used techniques in JavaScript. In this chapter, you find out how and why to pass functions as parameters to other functions.

Don’t forget to visit the website to check out the online exercises relevant to this chapter!

What Are Callbacks?

JavaScript functions are objects. This statement is the key to understanding many of the more advanced JavaScript topics, including callback functions.

Functions, like any other object, can be assigned to variables, be passed as arguments to other functions, and created within and returned from functions.

Passing functions as arguments

A callback function is a function that is passed as an argument to another function. Callback functions are a technique that’s possible in JavaScript ...