# Array in Javascript

In JavaScript, an array is a collection of values that are stored in a single variable. Arrays are created using square brackets, and the values inside the brackets are each separated by commas. In JavaScript array is a non-primitive datatype. It can be modified and is mutable.

Here's an example of an array that contains 4 elements:

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

You can access the elements of an array using their indexes. The index of the first elements starts from 0 and so on.

Here's an example of how to access the second element of the array:

```javascript
let myArray = [1, 2, 3];
let secondElement = myArray[1];  // secondElement is now 2
```

There are many methods available for working with arrays, such as `push` and `pop` for adding and removing elements, `shift` and `unshift` for adding and removing elements from the beginning of the array, and `sort` for sorting the elements.

### Array Methods in JavaScript :

Here is a list of some of the most commonly used methods for working with arrays in JavaScript:

1. `push`: adds one or more elements to the end of an array and returns the new length of the array.
    
2. `pop`: removes the last element from an array and returns the value of that element.
    
3. `shift`: removes the first element from an array and returns the value of that element.
    
4. `unshift`: adds one or more elements to the beginning of an array and returns the new length of the array.
    
5. `concat`: combines two or more arrays and returns a new array.
    
6. `slice`: returns a shallow copy of a portion of an array.
    
7. `splice`: adds or removes elements from an array.
    
8. `sort`: sorts the elements of an array in place and returns the sorted array.
    
9. `reverse`: reverses the order of the elements of an array in place and returns the reversed array.
    
10. `indexOf`: returns the index of the first occurrence of a specified element in an array, or -1 if the element is not present.
    
11. `lastIndexOf`: returns the index of the last occurrence of a specified element in an array, or -1 if the element is not present.
    
12. `forEach`: executes a provided function once for each array element.
    
13. `map`: creates a new array with the results of calling a provided function on every element in the array.
    
14. `filter`: creates a new array with all elements that pass the test implemented by a provided function.
    
15. `reduce`: applies a function against an accumulator and each element in the array (from left to right) to reduce it to a single value.
    
16. The `some()` method in JavaScript is used to test whether at least one element in an array passes a test implemented by a provided function. It returns a Boolean value of `true` if the provided function returns `true` for at least one element in the array, and `false` if it returns `false` for all elements.
    
17. The `find()` method in JavaScript is used to return the value of the first element in an array that satisfies a provided testing function. If no element passes the test, the `find()` method returns `undefined`.