20 JavaScript One‑Liner Tricks for Frontend Development

This article compiles twenty practical JavaScript one‑liner tricks aimed at improving front‑end development efficiency. Each trick includes a brief description and a ready‑to‑copy code snippet.

Get Browser Cookie Value

Use document.cookie to retrieve the value of a specific cookie.

const cookie = name => `;${document.cookie}`.split(`; ${name}=`).pop().split(';').shift();

cookie('_ga'); // Result: "GA1.2.1929736587.1601974046"

Convert RGB to Hex

Convert RGB color components to a hexadecimal string.

const rgbToHex = (r, g, b) => "#" + ((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1);

rgbToHex(0, 51, 255); // Result: #0033ff

Copy to Clipboard

Use navigator.clipboard.writeText to copy text to the clipboard.

const copyToClipboard = text => navigator.clipboard.writeText(text);

copyToClipboard("Hello World");

Check If Date Is Valid

Validate a date string using Date and Number.isNaN .

const isDateValid = (...val) => !Number.isNaN(new Date(...val).valueOf());

isDateValid("December 17, 1995 03:24:00"); // Result: true

Find Day of Year

Calculate which day of the year a given date falls on.

const dayOfYear = date => Math.floor((date - new Date(date.getFullYear(), 0, 0)) / 1000 / 60 / 60 / 24);

dayOfYear(new Date()); // Result: 272

Capitalize String

Transform the first character of a string to uppercase.

const capitalize = str => str.charAt(0).toUpperCase() + str.slice(1);

capitalize("follow for more"); // Result: Follow for more

Calculate Days Between Two Dates

Compute the absolute number of days between two dates.

const dayDif = (date1, date2) => Math.ceil(Math.abs(date1.getTime() - date2.getTime()) / 86400000);

dayDif(new Date("2020-10-21"), new Date("2021-10-22")); // Result: 366

Clear All Cookies

Remove all cookies by setting their expiration date to the past.

const clearCookies = document.cookie.split(';').forEach(cookie => document.cookie = cookie.replace(/^ +/, '').replace(/=.*/, `=;expires=${new Date(0).toUTCString()};path=/`));

Generate Random Hex Color

Create a random hexadecimal color string using Math.random and padEnd .

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

console.log(randomHex()); // Result: #92b008

Remove Duplicates From Array

Eliminate duplicate values in an array using Set .

const removeDuplicates = arr => [...new Set(arr)];

console.log(removeDuplicates([1,2,3,3,4,4,5,5,6])); // Result: [ 1, 2, 3, 4, 5, 6 ]

Get URL Query Parameters

Parse query parameters from a URL string.

const getParameters = URL => {
  URL = JSON.parse('{"' + decodeURI(URL.split("?")[1]).replace(/"/g, '\\"').replace(/&/g, '","').replace(/=/g, '":"') + "}"});
  return JSON.stringify(URL);
};

Extract Time From Date

Format a date object to hh:mm:ss using toTimeString .

const timeFromDate = date => date.toTimeString().slice(0, 8);

console.log(timeFromDate(new Date(2021, 0, 10, 17, 30, 0))); // Result: "17:30:00"

Check If Number Is Even

Determine whether a number is even.

const isEven = num => num % 2 === 0;

console.log(isEven(2)); // Result: True

Calculate Average of Numbers

Use reduce to compute the average of multiple numbers.

const average = (...args) => args.reduce((a, b) => a + b) / args.length;

average(1, 2, 3, 4); // Result: 2.5

Scroll to Top

Automatically scroll the page to the top.

const goToTop = () => window.scrollTo(0, 0);

goToTop();

Reverse String

Reverse a string using split , reverse , and join .

const reverse = str => str.split('').reverse().join('');

reverse('hello world'); // Result: 'dlrow olleh'

Check If Array Is Not Empty

Return true if an array exists and contains elements.

const isNotEmpty = arr => Array.isArray(arr) && arr.length > 0;

isNotEmpty([1,2,3]); // Result: true

Get Selected Text

Retrieve the currently selected text in the browser.

const getSelectedText = () => window.getSelection().toString();

getSelectedText();

Shuffle Array

Randomly reorder an array's elements.

const shuffleArray = arr => arr.sort(() => 0.5 - Math.random());

console.log(shuffleArray([1,2,3,4])); // Result: [ 1, 4, 3, 2 ]

Detect Dark Mode

Check whether the user's system prefers a dark color scheme.

const isDarkMode = window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches;

console.log(isDarkMode); // Result: True or False

The article concludes after presenting all twenty one‑liner tricks, hoping they help readers streamline daily front‑end tasks.