Top 10 JavaScript Array tricks

These are some of the very basic Javascript methods that will help you get better in Javascript. Let’s straightly jump into coding.. emoji-boom

Fill array with data

var myArray = new Array(10).fill('A');

['A', 'A', 'A', 'A', 'A', 'A', 'A', 'A', 'A', 'A'];

Every now and then we need to fill some array with any data. Here we are making use of the fill method from the Array API. Notice the count 10, it denotes the number of times to fill the content specified inside the fill() function.

Merge Arrays

var bikes = ['TVS', 'BMW', 'Ducati'];
var cars = ['Mercedes', 'Ford', 'Porsche'];
var autoMobiles = [...bikes, ...cars];

['TVS', 'BMW', 'Ducati', 'Mercedes', 'Ford', 'Porsche'];

Merging arrays are a major use case in any application that we develop. We might have user array and a permission array denoting permissions for the user. We might need to combile it as a array in order to perform something on the API. Here we are making use of the spread operator ... to combine or merge arrays.

Intersection of arrays

var setA = [5, 10, 4, 7, 1, 3];
var setB = [3, 11, 1, 10, 2, 6];
var duplicatedValues = [...new Set(setA)].filter((x) => setB.includes(x));

[10, 1, 3];

This is a crucial use case. Imagine a use case where where you need to find out the duplicated values from two arrays, or also called as intersection. We are first creating a unique array by combining the ... spread operator and Set function and then filter if the other array has those values.

Remove duplicates

var mixedArray = [12, 'web development', '', NaN, undefined, 0, true, false];
var whatIsTrue = mixedArray.filter(Boolean);

[12, 'web development', true];

We might need to filter falsy values like [0, undefined, null, false]. This is a simple trick to do so.

Get random value

var numbers = [];
for (let i = 0; i < 10; i++) {

var random = numbers[Math.floor(Math.random() * numbers.length)];


Need a random integer value ? No problem. In one line of code you can do so.

Reverse an Array

var reversedArray = numbers.reverse();

[9, 8, 7, 6, 5, 4, 3, 2, 1, 0];

These are just very basic built in functions to reverse the given array.

Sum of all values in array

var sumOfAllNumbers = numbers.reduce((x, y) => x + y);


Remove duplicates from array

var duplicatedArray = ['hello', 'hello', 'web developers'];
var nonDuplicatedArray = [...new Set(duplicatedArray)];

['hello', 'web developers'];

This is a super efficient way to remove duplicates from array. We combine ... spread operator and the Set() API, to achieve it.

Thanks for reading. I hope this gave you an some insights about the Javascript array methods. Keep following and Stay tuned for more amazing blogs.



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