20 Actually Useful JavaScript One-Liners (2026)

Q: Are there any limits to these one-liners?

Several skip edge-case validation for brevity. `chunk` uses reduce which creates intermediate arrays. `debounce` and `throttle` don't handle `this` binding in all cases — pass arrow functions and they work fine. For production, consider lodash equivalents where correctness matters more than line count.

DodaTech Updated 2026-06-20 3 min read

In this tutorial, you'll learn about 20 actually useful javascript one. We cover key concepts, practical examples, and best practices to help you understand and apply this topic effectively.

One-liners get a bad reputation as code-golf tricks. These aren't that. Each one solves a concrete daily problem — deduplicating arrays, cloning objects safely, debouncing input handlers, or Parsing URL parameters. They're short enough to memorize, practical enough to use every day.

Arrays

Deduplicate an array

const unique = arr => [...new Set(arr)];
unique([1, 2, 2, 3, 3, 4]); // [1, 2, 3, 4]

Remove falsy values

const compact = arr => arr.filter(Boolean);
compact([0, 1, false, 2, '', 3]); // [1, 2, 3]

Shuffle an array (Fisher-Yates)

const shuffle = arr => arr.map(v => ({ v, r: Math.random() })).sort((a, b) => a.r - b.r).map(v => v.v);
shuffle([1, 2, 3, 4, 5]); // [3, 1, 5, 2, 4] (random)

Chunk into groups

const chunk = (arr, size) => arr.reduce((acc, _, i) => i % size === 0 ? [...acc, arr.slice(i, i + size)] : acc, []);
chunk([1, 2, 3, 4, 5], 2); // [[1, 2], [3, 4], [5]]

Intersection of two arrays

const intersection = (a, b) => a.filter(v => b.includes(v));
intersection([1, 2, 3], [2, 3, 4]); // [2, 3]

Difference of two arrays (in a but not in b)

const difference = (a, b) => a.filter(v => !b.includes(v));
difference([1, 2, 3], [2, 3, 4]); // [1]

Flatten one level

const flatten = arr => arr.flat();
flatten([[1, 2], [3, 4]]); // [1, 2, 3, 4]

Flatten deeply (any depth)

const deepFlatten = arr => arr.flat(Infinity);
deepFlatten([1, [2, [3, [4]]]]); // [1, 2, 3, 4]

Objects

Deep clone without libraries

const deepClone = obj => structuredClone(obj);
// Browser-native, handles dates, arrays, maps, sets, circular refs

Pick specific keys

const pick = (obj, keys) => Object.fromEntries(keys.filter(k => k in obj).map(k => [k, obj[k]]));
pick({ a: 1, b: 2, c: 3 }, ['a', 'c']); // { a: 1, c: 3 }

Omit specific keys

const omit = (obj, keys) => Object.fromEntries(Object.entries(obj).filter(([k]) => !keys.includes(k)));
omit({ a: 1, b: 2, c: 3 }, ['b']); // { a: 1, c: 3 }

Group by key

const groupBy = (arr, fn) => arr.reduce((acc, v) => { const k = fn(v); (acc[k] ??= []).push(v); return acc; }, {});
groupBy([6.1, 4.2, 6.3], Math.floor); // { 4: [4.2], 6: [6.1, 6.3] }

Sort by key

const sortBy = (arr, key) => arr.sort((a, b) => a[key] > b[key] ? 1 : -1);
sortBy([{ n: 3 }, { n: 1 }, { n: 2 }], 'n'); // [{ n: 1 }, { n: 2 }, { n: 3 }]

Deep freeze an object

const deepFreeze = obj => { Object.keys(obj).forEach(k => typeof obj[k] === 'object' && deepFreeze(obj[k])); return Object.freeze(obj); };

Strings & Values

Random hex color

const randomHex = () => `#${Math.floor(Math.random() * 0xffffff).toString(16).padStart(6, '0')}`;
randomHex(); // #a3f7c2

Copy to clipboard

const copy = text => navigator.clipboard.writeText(text);
copy("Hello"); // Copies to clipboard

Detect dark mode

const isDarkMode = () => window.matchMedia('(prefers-color-scheme: dark)').matches;
isDarkMode(); // true or false

Async & DOM

Wait / delay

const wait = ms => new Promise(resolve => setTimeout(resolve, ms));
await wait(1000); // Waits 1 second

Debounce (with leading option)

const debounce = (fn, delay) => { let t; return (...args) => { clearTimeout(t); t = setTimeout(() => fn(...args), delay); }; };

Throttle

const throttle = (fn, limit) => { let inThrottle; return (...args) => { if (!inThrottle) { fn(...args); inThrottle = true; setTimeout(() => inThrottle = false, limit); } }; };

Parse URL parameters

const getParams = url => Object.fromEntries(new URL(url).searchParams);
getParams('https://example.com?a=1&b=2'); // { a: '1', b: '2' }

Is structuredClone() supported everywhere?

Yes — all modern browsers (Chrome 98+, Firefox 94+, Safari 15.4+) and Node 17+. It replaces JSON.parse(JSON.stringify(obj)) for deep cloning with better performance and support for Dates, Maps, Sets, and ArrayBuffers.

When should I use debounce vs throttle?

Debounce delays execution until after a pause — use for search-as-you-type inputs. Throttle limits execution rate — use for scroll or resize handlers where you want periodic updates.

Are there any limits to these one-liners?

Several skip edge-case validation for brevity. chunk uses reduce which creates intermediate arrays. debounce and throttle don't handle this binding in all cases — pass arrow functions and they work fine. For production, consider lodash equivalents where correctness matters more than line count.

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