JavaScript Array methods

Aug 1st 2020 ‧ 2 minutes read
#JavaScript

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.

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