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Define and Use the Functions

Define and Use the Functions

Learn to divide a program into functions or subprograms in JavaScript.

Function

We can divide a program into procedural components or modules called functions in JavaScript. We are already familiar with functions like console.log(), prompt(), and length(). Functions can be copied and reused in a programming technique called a modular or procedural approach, also known as the divide and conquer approach. We should always try to design functions that can be reused in other programs too.

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Broadly, there are two types of functions, which we’ll explore in the following sections.

Structure of a function

The following slides illustrate various parts of a function definition:

A function name can only contain letters (AZ and az) and the underscore symbol (_). It may also contain digits (09), but the function name can’t start with those. For example, Key_2 is a valid function name, but 2_key is not. Function names are case-sensitive, meaning that name, Name, and NAME are three different functions.

There are two main parts of a function definition:

  • Header: The first line, with a pair of brackets. ...