20+ Handy JavaScript Functions to Simplify Your Code | JavaScript Tutorial

JavaScript is a functional programming language, and functions play a crucial role. They allow you to encapsulate reusable code and perform specific tasks. Here are some quick examples of functions that can make your life easier:

Regular function

function sum(a, b) {
  return a + b;
}

Function expression

const sum = function (a, b) {
  return a + b;
};

Arrow function

const sum = (a, b) => {
  return a + b;
};
// OR
const sum = (a, b) => a + b;

Generator function

function* indexGenerator() {
  let index = 0;
  while (true) {
    yield index++;
  }
}
const g = indexGenerator();
console.log(g.next().value); // => 0
console.log(g.next().value); // => 1

Create an array of numbers from 1 to n

const range = (n) => Array.from({ length: n }, (_, i) => i + 1);
console.log(range(10)); // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Create an array of numbers from 1 to n with a step

const range = (n, step = 1) => Array.from({ length: n }, (_, i) => i * step);
console.log(range(10, 2)); // [1, 3, 5, 7, 9]

Create an array and fill it with a value

const fill = (len, value) => Array(len).fill(value);
console.log(fill(3, 0)); // [0, 0, 0]

Shuffling an array

const shuffleArray = (arr) => arr.sort(() => 0.5 - Math.random());
console.log(shuffleArray([1, 2, 3, 4])); // [3, 2, 1, 4]

Remove Duplicated from Array

const removeDuplicated = (arr) => [...new Set(arr)];
console.log(removeDuplicated([1, 2, 3, 3, 4, 4, 5, 5, 6])); // Result: [ 1, 2, 3, 4, 5, 6 ]

const removeDuplicate = (arr) =>
  Object.values(arr.reduce((a, b) => (a[b] ? a : { ...a, [b]: b }), {}));
console.log(removeDuplicate([1, 2, 3, 3])); // Result: [ 1, 2, 3, ]

Generate random number

const random = (min, max) => Math.floor(Math.random() * (max - min + 1)) + min;
console.log(random(1, 10)); // Result: 1 ~ 10

Find largest numbers

const findLargest = (arr) => arr.map((subArr) => Math.max(...subArr));
console.log(
  findLargest([
    [4, 5, 1, 3],
    [13, 27, 18, 26],
    [32, 35, 37, 39],
    [1000, 1001, 857, 1],
  ])
); // [5, 27, 39, 1001]

Find smallest numbers

const findSmallest = (arr) => arr.map((subArr) => Math.min(...subArr));
console.log(
  findSmallest([
    [4, 5, 1, 3],
    [13, 27, 18, 26],
    [32, 35, 37, 39],
    [1000, 1001, 857, 1],
  ])
); // [1, 18, 32, 857]

Pick a random element from an array

const pick = (arr) => arr[Math.floor(Math.random() * arr.length)];
console.log(pick([1, 2, 3, 4])); // 2

Convert array to object

const toObject = (arr) => ({ ...arr });
console.log(toObject(["a", "b"])); // { 0: 'a', 1: 'b' }

Find intersection of two arrays

const intersection = (arr1, arr2) => {
  const set = new Set(arr1);
  return arr2.filter((x) => set.has(x));
};
console.log(intersection([1, 2, 3], [2, 3, 4])); // [2, 3]

Remove falsy values from an array

const compact = (arr) => arr.filter(Boolean);
console.log(compact([0, 1, false, 2, "", 3, "a", "e" * 23, NaN, "s", 34])); // [1, 2, 3, 'a', 's', 34]

Reverse String

const reverseString = (str) => str.split("").reverse().join("");
console.log(reverseString("hello")); // olleh

Is String Palindrome

const isPalindrome = (str) => str === str.split("").reverse().join("");
console.log(isPalindrome("madam")); // true

Check object is empty or not

const isEmpty = (obj) => Object.keys(obj).length === 0;
console.log(isEmpty({})); // true

Find the number of days in a month

const getDaysInMonth = (date) =>
  new Date(date.getFullYear(), date.getMonth() + 1, 0).getDate();
console.log(getDaysInMonth(new Date())); // 31

Generate a random color

const getRandomColor = () =>
  `#${Math.floor(Math.random() * 16777215).toString(16)}`;
console.log(getRandomColor()); // #f0f0f0

const randomHex = () =>
  `#${Math.floor(Math.random() * 0xffffff)
    .toString(16)
    .padEnd(6, "0")}`;
console.log(randomHex()); // #f0f0f0

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Comments

[Tom Carter]

Nice list, but that shuffle function is not good and should be avoided. You can read all about the problems here: robweir.com/blog/2010/02/microsoft...

[Joseph42A]

Nice well done, just find a shorter way to build array from (n) numbers
Array.from(Array(n).keys())

[Pierre-Henry Soria ✨]

Nice list Rahul 🙂

[Wemmerson Albuquerque]

Nice! It reminded me of coding marathons =D

[Timothy Joseph Eslabra]

this will help me a lot on learning JavaScript thank you so much Rahul <3

[MexiKode ⚙]

generate cache-busting parameter for assets
let v = Date.now();

find needle in any string, example in path
if(top.location.href.includes('/blog')) //is in blog post view

get name of uri hash
let section = top.location.hash.substr(1);

[MexiKode ⚙]

var kkeys = [], konami = "38,38,40,40,37,39,37,39,66,65";
window.addEventListener("keydown", function(e){
kkeys.push( e.keyCode );
if ( kkeys.toString().indexOf( konami ) >= 0 )
kkeys = [];
}, true);

99 lives

[TUSHAR MALHOTRA]

function shuffleArray(new_arr) {
for (let i = new_arr.length - 1; i >= 0; i--) {
const j = Math.floor(Math.random() * (i + 1));
[new_arr[i], new_arr[j]] = [new_arr[j], new_arr[i]];
}
return new_arr;

}

console.log(shuffleArray(new_arr)); For shuffling array