19个 JavaScript 单行代码技巧，让你看起来像个专业人士

const randomString = () => Math.random().toString(36).slice(2)
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randomString() // gi1qtdego0b
randomString() // f3qixv40mot
randomString() // eeelv1pm3ja
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const escape = (str) => str.replace(/[&<>"']/g, (m) => ({ '&': '&', '<': '<', '>': '>', '"': '"', "'": ''' }[m]))
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escape('<div class="medium">Hi Medium.</div>') 
// <div class="medium">Hi Medium.</div>
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const uppercaseWords = (str) => str.replace(/^(.)|\s+(.)/g, (c) => c.toUpperCase())
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uppercaseWords('hello world'); // 'Hello World'
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const uppercaseWords = (str) => str.replace(/^(.)|\s+(.)/g, (c) => c.toUpperCase())
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const toCamelCase = (str) => str.trim().replace(/[-_\s]+(.)?/g, (_, c) => (c ? c.toUpperCase() : ''));
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toCamelCase('background-color'); // backgroundColor
toCamelCase('-webkit-scrollbar-thumb'); // WebkitScrollbarThumb
toCamelCase('_hello_world'); // HelloWorld
toCamelCase('hello_world'); // helloWorld
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const removeDuplicates = (arr) => [...new Set(arr)]
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console.log(removeDuplicates([1, 2, 2, 3, 3, 4, 4, 5, 5, 6])) 
// [1, 2, 3, 4, 5, 6]
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const flat = (arr) =>
    [].concat.apply(
        [],
        arr.map((a) => (Array.isArray(a) ? flat(a) : a))
    )
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// Or
const flat = (arr) => arr.reduce((a, b) => (Array.isArray(b) ? [...a, ...flat(b)] : [...a, b]), [])
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flat(['cat', ['lion', 'tiger']]) // ['cat', 'lion', 'tiger']
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const removeFalsy = (arr) => arr.filter(Boolean)
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removeFalsy([0, 'a string', '', NaN, true, 5, undefined, 'another string', false])
// ['a string', true, 5, 'another string']
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const isEven = num => num % 2 === 0
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isEven(2) // true
isEven(1) // false
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const random = (min, max) => Math.floor(Math.random() * (max - min + 1) + min)
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random(1, 50) // 25
random(1, 50) // 34
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const average = (...args) => args.reduce((a, b) => a + b) / args.length;
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average(1, 2, 3, 4, 5);   // 3
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const round = (n, d) => Number(Math.round(n + "e" + d) + "e-" + d)
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round(1.005, 2) //1.01
round(1.555, 2) //1.56
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const diffDays = (date, otherDate) => Math.ceil(Math.abs(date - otherDate) / (1000 * 60 * 60 * 24));
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diffDays(new Date("2021-11-3"), new Date("2022-2-1"))  // 90
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const dayOfYear = (date) => Math.floor((date - new Date(date.getFullYear(), 0, 0)) / (1000 * 60 * 60 * 24))
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dayOfYear(new Date()) // 74
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const randomColor = () => `#${Math.random().toString(16).slice(2, 8).padEnd(6, '0')}`
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randomColor() // #9dae4f
randomColor() // #6ef10e
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const rgbToHex = (r, g, b) => "#" + ((1 << 24) + (r << 16) + (
g << 8) + b).toString(16).slice(1)
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rgbToHex(255, 255, 255)  // '#ffffff'
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const clearCookies = () => document.cookie.split(';').forEach((c) => (document.cookie = c.replace(/^ +/, '').replace(/=.*/, `=;expires=${new Date().toUTCString()};path=/`)))
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const isDarkMode = window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches
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[foo, bar] = [bar, foo]
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const pause = (millis) => new Promise(resolve => setTimeout(resolve, millis))
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const fn = async () => {
  await pause(1000)
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console.log('fatfish') // 1s later
}
fn()
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