Course Content

Introduction to JavaScript

1. JavaScript Fundamentals

About JavaScript Understanding JavaScript Syntax Challenge: Console Output in JavaScript Using Comments to Document Code Challenge: Write a Single-Line Comment Challenge: Write a Multi-Line Comment

2. Variables and Data Types in JavaScript

Understanding Variables in JavaScript Challenge: Define the Variable Using const for Constants Exploring JavaScript Data Types Working with null in JavaScript Introduction to Arrays Array Methods and Manipulation Challenge: Perform Array Operations

3. Performing Operations in JavaScript

Understanding Assignment Operators Mathematical Operations in JavaScript Assignment Operators in JavaScript Increment and Decrement Operators Challenge: Variable Operations Practice Comparison Operators in JavaScript Logical Operators Explained Challenge: Compare Variables in JavaScript Concatenating Strings in JavaScript Challenge: Build Sentences with JavaScript

4. Controlling Program Flow with Conditional Statements

Mastering if Statements in JavaScript Using else for Alternative Outcomes Applying else if for Multiple Conditions Challenge: Determine Sizes with Conditionals

5. Looping Through Data in JavaScript

Understanding the while Loop in JavaScript Using the do while Loop for Iteration Challenge: Print Numbers from 5 to 9 Mastering the for Loop in JavaScript Challenge: Console Tigers with Loops Breaking Out of Loops with break Skipping Iterations with continue Challenge: Stop and Skip in Loops

6. Functions in JavaScript

What Are Functions in JavaScript?Defining Functions in JavaScript Challenge: Write a Function – My Name Using Function Arguments Effectively Returning Values from Functions Challenge: Create a Sum Function Course Summary & Next Steps

Introduction to Arrays

The array is the most useful data structure.

Note

A data structure is a specialized format for organizing and working with data collection. An array is a collection of items where each item is a value.

Creating an Array

To create an array, use square brackets []:

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This creates an empty array with no elements. To create an array with elements, place the elements inside [] and separate them with commas (,):

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Note

The last element in the array should not have a comma after it.

To print an array, simply use console.log():


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const arr = [1, 2, 3, 4, 5];

console.log(arr);

Indexes

Each element in an array has a unique index.

Note

Indexes start from 0. The first element has an index of 0, the second element has an index of 1, and so on.

Accessing array data is done by specifying the index in square brackets ([index]) after the array name:

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const arr = [1, 2, 3, 4, 5];

const thirdElement = arr[2];  // retrieving the 3rd element

console.log(thirdElement);

Arrays can hold different data types, including number, string, boolean, and more.


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const arr = [2441.23, "Hello!", false];

console.log(arr[0]);
console.log(arr[1]);
console.log(arr[2]);

Length Property

The length property is a built-in property of arrays that represents the number of elements in that array. To use this property, use the following syntax:

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const arr1 = [10, 20, 30];
const arr2 = [15, 25, 35, 45, 55];

const x = arr1.length; // `x` variable represents the `arr1` length
const y = arr2.length; // `y` variable represents the `arr2` length

console.log(x);
console.log(y);

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Section 2. Chapter 6

Introduction to JavaScript

Introduction to Arrays

Creating an Array

Indexes

Length Property

1. Which brackets are used to create an array?

2. Retrieve the second element from the array:

3. How do you get the length of the array?