10 JavaScript One-Liners Every Developer Should Know

These aren't just clever tricks — they're practical patterns you'll reach for daily.

1. Remove Duplicates from an Array

const unique = [...new Set(array)];

Works with primitives (strings, numbers). For objects, you'll need a different approach.

2. Generate a Random UUID

const uuid = crypto.randomUUID();
// "3b241101-e2bb-4d52-8f4a-6e9d2ed35c21"

Built into all modern browsers — no library needed.

3. Copy Text to Clipboard

await navigator.clipboard.writeText("Hello, clipboard!");

Requires user interaction (click/keypress) and HTTPS.

4. Shuffle an Array

const shuffled = array.sort(() => Math.random() - 0.5);

Good enough for most cases. For truly unbiased shuffling, use Fisher-Yates.

5. Get a Random Element

const random = array[Math.floor(Math.random() * array.length)];

6. Flatten a Nested Array

const flat = array.flat(Infinity);
// [1, [2, [3, 4]]] → [1, 2, 3, 4]

7. Check if an Element is in the Viewport

const isVisible = (el) => {
  const r = el.getBoundingClientRect();
  return r.top < window.innerHeight && r.bottom > 0;
};

8. Debounce a Function

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

Okay, this one is two lines. But it saves you from installing lodash.

9. Deep Clone an Object

const clone = structuredClone(original);

Native deep cloning — handles dates, maps, sets, and circular references. Finally no more JSON.parse(JSON.stringify(...)) hacks.

10. Group an Array by Key

const grouped = Object.groupBy(items, (item) => item.category);

Object.groupBy is a newer API (2024+). Falls back to a reduce for older environments:

const grouped = items.reduce((acc, item) => {
  (acc[item.category] ??= []).push(item);
  return acc;
}, {});

These one-liners are the kind of thing you learn once and use forever. Bookmark this page and come back to it when you need a quick reference.

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