Array in JavaScript

An Array is an object type designed for storing data collections.

Key characteristics of JavaScript arrays are:

• Elements: An array is a list of values, known as elements.
• Ordered: Array elements are ordered based on their index.
• Zero indexed: The first element is at index 0, the second at index 1, and so on.
• Dynamic size: Arrays can grow or shrink as elements are added or removed.
• Heterogeneous: Arrays can store elements of different data types (numbers, strings, objects and other arrays).

Why Use Arrays?

If you have a list of items (a list of car names, for example), storing the names in single variables could look like this:

           let car1 = "Saab";
           let car2 = "Volvo";
           let car3 = "BMW";

However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?

The solution is an array!

An array can hold many values under a single name, and you can access the values by referring to an index number.

Creating an Array

Using an array literal is the easiest way to create a JavaScript Array.

Syntax:

const array_name = [item1, item2, ...];

It is a common practice to declare arrays with the const keyword.

You can also create an empty array, and provide elements later:

Using the JavaScript Keyword new

The following example also creates an Array, and assigns values to it:

The two examples above do exactly the same.

There is no need to use new Array().

For simplicity, readability and execution speed, use the array literal method.

Accessing Array Elements

You access an array element by referring to the index number:

const cars = ["Saab", "Volvo", "BMW"];
let car = cars[0];

Changing an Array Element

This statement changes the value of the first element in cars:

const cars = ["Saab", "Volvo", "BMW"];
cars[0] = "Opel";