https://github.com/airbnb/javascript?utm_source=gold_browser_extension
1. build up string
// bad function sayHi(name) { return 'How are you, ' + name + '?'; } // bad function sayHi(name) { return ['How are you, ', name, '?'].join(); } // bad function sayHi(name) { return `How are you, ${ name }?`; } // good function sayHi(name) { return `How are you, ${name}?`; }
2. copy array
// bad const len = items.length; const itemsCopy = []; let i; for (i = 0; i < len; i += 1) { itemsCopy[i] = items[i]; } // good const itemsCopy = [...items];
3. Use array destructuring
const arr = [1, 2, 3, 4]; // bad const first = arr[0]; const second = arr[1]; // good const [first, second] = arr;
4. Use object destructuring for multiple return values, not array destructuring.
// bad function processInput(input) { // then a miracle occurs return [left, right, top, bottom]; } // the caller needs to think about the order of return data const [left, __, top] = processInput(input); // good function processInput(input) { // then a miracle occurs return { left, right, top, bottom }; } // the caller selects only the data they need const { left, top } = processInput(input);
5. Use default parameter syntax rather than mutating function arguments.
// really bad function handleThings(opts) { // No! We shouldn’t mutate function arguments. // Double bad: if opts is falsy it'll be set to an object which may // be what you want but it can introduce subtle bugs. opts = opts || {}; // ... } // still bad function handleThings(opts) { if (opts === void 0) { opts = {}; } // ... } // good function handleThings(opts = {}) { // ... }
6. function params
// good const itemHeight = (item) => { const { height, largeSize, smallSize } = item; return height > 256 ? largeSize : smallSize; }; // good const itemHeight = ( { height, largeSize, smallSize } ) => { return height > 256 ? largeSize : smallSize; };
7. Always use class
. Avoid manipulating prototype
directly.
// bad function Queue(contents = []) { this.queue = [...contents]; } Queue.prototype.pop = function () { const value = this.queue[0]; this.queue.splice(0, 1); return value; }; // good class Queue { constructor(contents = []) { this.queue = [...contents]; } pop() { const value = this.queue[0]; this.queue.splice(0, 1); return value; } }
8. Use extends
for inheritance.
// bad const inherits = require('inherits'); function PeekableQueue(contents) { Queue.apply(this, contents); } inherits(PeekableQueue, Queue); PeekableQueue.prototype.peek = function () { return this.queue[0]; }; // good class PeekableQueue extends Queue { peek() { return this.queue[0]; } }