August 2022
Beginner
912 pages
19h 57m
English
Content preview from Coding All-in-One For Dummies, 2nd Edition
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Chapter 13
Understanding Callbacks and Closures
IN THIS CHAPTER
Understanding callback functions
Using callbacks
Creating closures
“O, call back yesterday, bid time return.”
— EARL OF SALISBURY, RICHARD II
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 arguments to other functions.
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 because of the fact that functions are objects.
Function objects contain a string with the code of the function. When you call a function by naming the function, followed by (), you're telling ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.