The **array** is the most useful data structure.

> Note
>
> **Data Structure** is a specialized format for working with a data set (data organization).
>
> **Array** is an item collection where items are literals.

# Creating
To create an array you need to use `[]`:

```javascript
let arr = [];
```

It's the array without elements (empty array). To create an array with elements, you should put elements into `[]` and separate them with commas (`,`):

```javascript
let arr = [1, 2, 3, 4, 5];
```

> Note
>
> There should be no comma after the last element of the array.

You can print the array by `console.log()`:

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

console.log(arr);

# Indexes
Every element in the array has a unique index:

> Note
>
> Indexes start from **0**. The first element is placed with the index **0**, the second element is placed with the index **1**, etc.
>
> To calculate the index of an element, you can use the formula "**N - 1**" (where **N** is the number of the element).

You have access to the array data by index. You can retrieve an element from the array simply by writing its index in square brackets (`[index]`) after the array name:

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

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

console.log(element);

Arrays in JS can work with different data types: **number**, **string**, **boolean**, etc.

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

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

# Length
The `length` is a **property**. The `length` returns an array length:

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

let x = arr1.length;  // save arr1 length to variable `x`
let y = arr2.length;  // save arr2 length to varialbe `y`

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

> Note
>
> **Property** and **Method** concepts is used in **Object-Oriented Programming (OOP)**. This will be described in another course.
>
> **Methods** are called like functions using parentheses `()`, while **properties** provide values like variables.

Which brackets are used to create an array?

First, let's get acquainted with JavaScript and look at its syntax. In this section, you will get a basic familiarity with the JavaScript syntax to make it easier to learn in detail later on.

Now it's time to learn about the data types that JavaScript works with. We'll start by looking at the difference between literals and variables, and then delve into the various data types.

We have become familiar with the various data types. Now, let's learn how to work with them by learning the operations we can perform with each data type.

Next, we will learn how to control the flow of execution. It's a straightforward process: we can tell the interpreter exactly what to do under certain conditions.

Next, we will explore how to shorten code using repetitive looped actions. We will examine the types of loops available in JavaScript and learn how to work with them.

Finally, to be able to write simple programs, we need to learn about functions that can make our lives much easier. We will learn how to create and use our functions.

Creating

Indexes

Length

Which brackets are used to create an array?

Retrieve second element from the array:

How to get the length of the array?