Section 1.1: Introduction to Arrays

Let’s begin by delving into what an array is in JavaScript. Unlike a single variable, which can hold just one value—like an integer or a string—arrays allow us to store multiple values in a single variable.

For instance, you can declare a variable like this:

let name = "Nitin";

But if you want to keep track of several values, you’ll need an array.

Array Declaration:

There are primarily two ways to declare an array in JavaScript. The first is through the Array constructor:

let array = new Array();

For example:

let countries = new Array("USA", "India", "England");

console.log(countries);

// Output: ["USA", "India", "England"]

Now, let’s look at the second method for declaring an array. First, we can create an empty array:

let array = [];

For instance:

let countries = ["USA", "India", "England"];

console.log(countries);

// Output: ["USA", "India", "England"]

Section 1.2: Accessing Array Elements

Accessing an element from an array refers to retrieving a specific item. Remember that array indexing starts at zero.

For example:

let countries = ["USA", "India", "England"];

console.log(countries[0]);

// Output: USA

Here, we define an array named countries and print the value at index 0, which is "USA". You can access each element similarly:

console.log(countries[0]); // USA

console.log(countries[1]); // India

console.log(countries[2]); // England

Section 1.3: Adding Elements to an Array

Inserting a new element into an array is done using the push() method, which adds an item to the end of the array.

For instance:

let countries = ["USA", "India", "England"];

countries.push("Russia");

console.log(countries);

// Output: ["USA", "India", "England", "Russia"]

Initially, we have three countries. After using the push method to add "Russia", the output becomes ["USA", "India", "England", "Russia"].

You can also insert multiple items at once:

countries.push("Italy", "Germany", "France", "Australia");

console.log(countries);

// Output: ["USA", "India", "England", "Russia", "Italy", "Germany", "France", "Australia"]

Here’s a breakdown of the indexes in the countries array:

• Index 0: "USA"
• Index 1: "India"
• Index 2: "England"
• Index 3: "Russia"
• Index 4: "Italy"
• Index 5: "Germany"
• Index 6: "France"
• Index 7: "Australia"

To access an element, simply use its index. For instance, console.log(countries[3]); will display "Russia".

Section 1.4: Removing Elements from an Array

JavaScript allows us to remove an element from an array using the pop() method, which deletes the last item.

For example:

let countries = ["USA", "India", "England"];

countries.pop();

console.log(countries);

// Output: ["USA", "India"]

If you try to add an element inside the pop() method, it won’t work as intended; it will still remove the last element.

For example:

countries.pop("USA");

console.log(countries);

// Output: ["USA", "India"]

Section 1.5: Where to Practice

Many of you likely have Google Chrome. You can practice JavaScript there easily:

1. Open Google Chrome.
2. Press Ctrl+Shift+I (on Windows or Mac) to open the developer tools.
3. Navigate to the Console tab.
4. Write your JavaScript code and execute it.
5. Use Shift+Enter for a new line, and hit Enter to run your code.