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Ishaan Sheikh

Posted on • Updated on • Originally published at frikishaan.com

# JavaScript Array methods

In this post, we will learn some of the arrays methods available in JavaScript.

### 1. Array.sort()

This method sorts the items of the array. It takes an optional `compareFunction` in which you can define your own criteria for sorting.

Syntax

``````array.sort(compareFunction)
``````

Example

``````var numbers = [3,6,1,0,9];
console.log(numbers.sort()); // [0,1,3,6,9]
``````

Using `compareFunction` to sort in descending order.

``````var numbers = [3,6,1,0,9];
console.log(numbers.sort((a, b) => (a > b ? -1 : 1))); // [9,6,3,1,0]
``````

### 2. Array.slice()

This method used to get the array of elements from a given position to a given position in an array. Both parameters are optional in this function.

Syntax

``````array.slice(start, end)
``````

Example

``````var numbers = [1,2,3,4,5];
console.log(numbers.slice(2,4)); // [3,4]

console.log(numbers.slice(3)); // [4,5]
``````

### 3. Array.filter()

The `filter()` method in javascript is used to filter the elements present in the array based on the condition. It takes a mandatory function as an argument in which we define our filtering criteria.

Syntax

``````array.filter(function(element) { return condition: })
``````

Example

``````var numbers = [1,2,3,4,5];

console.log(numbers.filter((element) => element % 2 == 0)); //[2,4]
``````

In the above example, the filter function returns only even numbers.

### 4. Array.reverse()

The `reverse()` function in javascript reverses the order of elements in an array.

Syntax

``````array.reverse()
``````

Example

``````var cars = ["Audi", "Ford", "BMW"];
console.log(cars.reverse()); // ["BMW", "Ford", "Audi"]
``````

### 5. Array.includes()

This method is used to check whether the array contains an element or not. It returns `true` if the element exists in the array and `false` otherwise.

Syntax

``````array.includes(element, start);
``````

The `start` is an optional argument, it defines at which index should the searching should starts.

Example

``````var cars = ["Audi", "Ford", "BMW"];

console.log(cars.includes("Tesla")); // false
``````

### 6. Array.concat()

This method is used to join two or more arrays into a single array.

Syntax

``````array1.concat(array2, array3,....arrayN);
``````

Example

``````var cars = ["Audi", "Tesla", "BMW"];
var numbers = [1,2,3];

console.log(cars.concat(numbers)); // ["Audi", "Tesla", "BMW", 1, 2, 3]
``````

## Bonus

Array.prototype constructor

It allows us to add new properties and methods to the Array Object.

Syntax

``````Array.prototype.yourProperty = value;

Array.prototype.yourMethod = function () {
console.log(this); // this refers to the array
};
``````

In this post, I showed you some of the array methods. If you want to learn about more javascript array functions consider watching this series of videos by Florin Pop. In this series, he has explained about 24 javascript array methods.

## Discussion (2)

Matt Ellen • Edited on

It might be worth mentioning that `sort` without a comparison function sorts by converting the elements to strings and using string comparison, so `[3,7,2,1,35,24].sort()` will end up as `[1,2,24,3,35,7]`.

Ishaan Sheikh

Thanks for pointing out.