JavaScript Cheat Sheet

const name = 'Workshelve';
let count = 0;

Use const by default and let when reassignment is required.

function greet(name) {
  return `Hello, ${name}`;
}

Function declarations are hoisted and work well for named reusable logic.

const double = (value) => value * 2;

Arrow functions are concise and keep lexical this binding.

const tools = ['Base64', 'JSON', 'YAML'];
const upper = tools.map((item) => item.toUpperCase());

Use map, filter, and reduce for data transformation.

const tool = { id: 'json-parser', active: true };
const { id, active } = tool;

Destructuring makes object access shorter and clearer.

const city = user?.profile?.address?.city ?? 'Unknown';

Optional chaining prevents crashes when intermediate values are missing.

async function loadTools() {
  const response = await fetch('/api/tools');
  const data = await response.json();
  return data;
}

Use async/await inside an async function, or at top level in a JavaScript module, to write asynchronous code in a readable sequence.

fetch('/api/tools')
  .then((response) => response.json())
  .then((data) => console.log(data));

Promise chains are still useful when composing async steps directly.

const message = `Loaded ${count} tools.`;

Template literals support interpolation and multiline strings.

export function formatName(value) {
  return value.trim();
}

import { formatName } from './format';

Use named exports for reusable utilities and explicit imports.

const text = JSON.stringify(payload, null, 2);
const parsed = JSON.parse(text);

Stringify serializes structured data; parse restores it.

const ids = new Set(['a', 'b']);
const lookup = new Map([['json', 'ready']]);

Sets help with uniqueness; Maps help with keyed lookups.