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.
Top comments (2)
It might be worth mentioning that
sortwithout 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].Thanks for pointing out.