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## Introduction to JavaScript

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1. JavaScript: Basics
9Topics
|
10 Quizzes
2. JavaScript: Variables
9Topics
|
10 Quizzes
3. JavaScript: Conditional Statements
10Topics
|
11 Quizzes
4. JavaScript: Functions
10Topics
|
11 Quizzes
5. JavaScript: Scope
6Topics
|
7 Quizzes
6. JavaScript: Arrays
11Topics
|
12 Quizzes
7. JavaScript: Loops
8Topics
|
9 Quizzes
8. JavaScript: High Order Functions
3Topics
|
4 Quizzes
9. JavaScript: Iterators
1Topic
|
1 Quiz

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Lesson 4, Topic 1
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# JavaScript: Introduction to Functions

##### Yasin Cakal 5 Nov 2021
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When learning how to calculate the perimeter of a square, there are a few steps to follow in order to get the right answer:

1. Take measurement of the square’s length.
2. Multiply the length with 4.

With practice, you’ll be able to calculate the perimeter of the square without needing to be guided through these two steps each time. The following code can be used to calculate the perimeter of a square:

``````const length= 10;
const perimeter=  length*4;
console.log(perimeter);

//40``````

Consider the following scenario: You’ve been asked to calculate the perimeter of three different squares:

``````//Perimeter of first square
var length= 12;
var perimeter=  length*4;
console.log(perimeter);

//Perimeter of second square
var length= 18;
var perimeter=  length*4;
console.log(perimeter);

//Perimeter of third square
var length= 19;
var perimeter=  length*4;
console.log(perimeter);

//Output: 48 72  76``````

In programming, we frequently use code to perform a task multiple times. Rather than rewriting the same code, we can group a block of code and associate it with a single task, then reuse that block of code whenever the task is repeated. This is accomplished through the use of a `function`. A `function` is a reusable code block that combines a series of statements to accomplish a specific task.

This lesson will teach you how to create functions and use them to write clearer and more concise code.

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