JavaScript Essentials For Dummies

Chapter 5

Harnessing the Power of Functions

IN THIS CHAPTER

Getting to know JavaScript functions

Creating and using custom functions

Passing and returning function values

Working with anonymous and arrow functions

Almost every JavaScript project beyond the simplest scripts will require one or more (usually a lot more) tasks or calculations that aren’t part of the JavaScript language or any Web API. What’s a coder to do? You roll up your sleeves and then roll your own code that accomplishes the task or runs the calculation.

This chapter shows you how to create such do-it-yourself code. In the pages that follow, you explore the powerful and infinitely useful realm of custom functions, where you craft reusable code that performs tasks that out-of-the-box JavaScript can’t do.

Getting to Know the Function Structure

A function is a group of JavaScript statements that are separate from the rest of the script and that perform a designated task. When your script needs to perform that task, you tell it to run — or execute, in the vernacular — the function.

The basic structure of a function ...