# JavaScript Arrays : The Basics

Think of JavaScript Arrays as that list where you can write down a number of things you want to do or buy, small list or a large list, related or unrelated.

## What is a JavaScript Array
An array is simply a type of JavaScript data structures that enables the nesting of elements in a collection under a named variable. 

```
let computers = [element1, element2, ……];
    //   variable      array with nested elements
```

## Creating an Array
You can declare or create an array by using the square brackets ‘[]’ using a variable and then separating elements using a comma(,).
You can do this using the array literal notation or the array constructor

### Formula for creating an array
```
variable arrayName = [element1, element2, element3........]
```
```

const computers = [“hp”, “apple”, “dell”]; // array literal notation
const computers = newArray [“hp”, “apple”, “dell”]; // array constructor
```
## Two-dimensional/ Multi-dimensional arrays
You can either have two-dimensional arrays or arrays nested in other arrays which are referred to as a multi-dimensional array.

```
const computers= [“hp”, “apple”, “dell”]; // two dimensional arrays
const computers = [“hp”, “apple”, [“dell”, “compaq”] ]; //multidimensional array
```

## To determine the Length of an array
The length property is simply used to count elements in an array. 
```
const computers = [“hp”, “apple”, “dell”]; 
console log(computers.length); // prints 3
```

## Accessing Arrays with Indexes
Arrays make use of the zero-index numbering system like the strings, you can easily access elements in the array. This simply means, the first element in an array is the zero(0) element.

```
const computers = [“hp”, “apple”, “dell”]
console.log(computers[0]) // prints hp since it’s the first element 
console.log(computers[1]) // prints apple since it’s the second element 
console.log(computers[2] // prints dell since it's the third elemet
``` 

Arrays are mutable and dynamically sized so elements in an array can be arranged in any order. and can be of any size. Arrays have built-in methods that make it easy to manipulate the values of elements, add, remove and even change their position. 

## Array Methods
###  Adding elements to Array

When adding elements to an array, you can use the unshift()method or the push() method.

The ```unshift()``` method adds elements to the beginning of an array.
```
const computers = [“hp”, “apple”, “dell”];
computers.unshift(“toshiba” , “compaq”);
console.log(computers); // prints toshiba, compaq, hp, apple, dell
```

The ```
push()
``` method adds elements to the end of an array.

```
const computers = [“hp”, “apple”, “dell”];
computers.push(“toshiba” , “compaq”);
console.log(computers); // prints hp, apple, dell,  toshiba, compaq
```

### Removing elements from an array
The ```
shift()
```method removes elements from the beginning of an array.
```
const computers = [“hp”, “apple”, “dell”];
computers.shift();
console.log(computers); // prints apple, dell since hp has been removed
```
The```
push()
``` method removes elements from the end of an array.
```
const computers = [“hp”, “apple”, “dell”];
computers.push();
console.log(computers); // prints hp, apple since dell has been removed

```

### Merging Two Arrays

You can easily merge two arrays with the  ```concat()``` method. This method merges two arrays creating a new array with the merged elements, leaving the individual arrays themselves unmerged.

```
const letters1 = [A B, C];
const letters2 = [D, E, F];
const letters3 = letters1.concat(letters2);
console.log(letters3); // prints A, B, C, D, E, F]// letters1 and letters2 still remain unchanged
```
### The splice() and slice() method

The ```
splice()
``` method can be used to add or remove any number of elements in a row from anywhere in an array. This method can add or remove up to three(3) elements from an array and create a new array for the removed elements.

```
const letters = [A, B, C, D, E, F];
const splicedItems = letters.splice(3, 2); // this means at index 3, delete 2 elements
console.log(splicedItems) = [C, D]
console.log(letters)=[A, B, E, F]
```


The ```
slice()
```method is used to copy a selected number of elements to a new array without changing the old array. You can use this method to copy or extract more than two(2) elements at a time.

```
const letters = [A, B, C, D, E, F];
const slicedItems = letters.slice(3, 2); // this means at index 3, copy 2 elements
console.log(slicedItems) = [C, D]
console.log(letters)=[A, B, C, D, E, F] // remains unchanged
```
You can now easily create, resize, edit arrays.  There are also [more advanced methods](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array) that perform other functions in JavaScript Arrays . I hope these tips aid with better understanding of arrays. 

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