JavaScript 单行功能代码

1、生成随机字符串

const randomString = () => Math.random().toString(36).slice(2)
randomString() // gi1qtdego0b
randomString() // f3qixv40mot
randomString() // eeelv1pm3ja

2、转义HTML特殊字符

const escape = (str) => str.replace(/[&<>"']/g, (m) => ({ '&': '&', '<': '<', '>': '>', '"': '"', "'": ''' }[m]))
escape('<div class="medium">Hi Medium.</div>') 
// &lt;div class=&quot;medium&quot;&gt;Hi Medium.&lt;/div&gt

3、字符串中每个单词的第一个字符大写

const uppercaseWords = (str) => str.replace(/^(.)|\s+(.)/g, (c) => c.toUpperCase())
uppercaseWords('hello world'); // 'Hello World'

4、将字符串转换为camelCase

const toCamelCase = (str) => str.trim().replace(/[-_\s]+(.)?/g, (_, c) => (c ? c.toUpperCase() : ''));
toCamelCase('background-color'); // backgroundColor
toCamelCase('-webkit-scrollbar-thumb'); // WebkitScrollbarThumb
toCamelCase('_hello_world'); // HelloWorld
toCamelCase('hello_world'); // helloWorld

5、数组去重

const removeDuplicates = (arr) => [...new Set(arr)]
console.log(removeDuplicates([1, 2, 2, 3, 3, 4, 4, 5, 5, 6])) 
// [1, 2, 3, 4, 5, 6]

6、展平一个数组

const flat = (arr) =>
    [].concat.apply(
        [],
        arr.map((a) => (Array.isArray(a) ? flat(a) : a))
    )
// Or
const flat = (arr) => arr.reduce((a, b) => (Array.isArray(b) ? [...a, ...flat(b)] : [...a, b]), [])
flat(['cat', ['lion', 'tiger']]) // ['cat', 'lion', 'tiger']

7、从数组中删除虚假值

const removeFalsy = (arr) => arr.filter(Boolean)
removeFalsy([0, 'a string', '', NaN, true, 5, undefined, 'another string', false])
// ['a string', true, 5, 'another string']

8、检查一个数字是偶数还是奇数

const isEven = num => num % 2 === 0
isEven(2) // true
isEven(1) // false

9、获取参数的平均值

const average = (...args) => args.reduce((a, b) => a + b) / args.length;
average(1, 2, 3, 4, 5);   // 3

10、将数字截断为固定小数点

const round = (n, d) => Number(Math.round(n + "e" + d) + "e-" + d)
round(1.005, 2) //1.01
round(1.555, 2) //1.56

11、计算两个日期相差天数

const diffDays = (date, otherDate) => Math.ceil(Math.abs(date - otherDate) / (1000 * 60 * 60 * 24));
diffDays(new Date("2021-11-3"), new Date("2022-2-1"))  // 90

12、将RGB颜色转换为十六进制

const rgbToHex = (r, g, b) => "#" + ((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1)
rgbToHex(255, 255, 255)  // '#ffffff'

13、检测暗模式

const isDarkMode = window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches

14、暂停一会

const pause = (millis) => new Promise(resolve => setTimeout(resolve, millis))
const fn = async () => {
  await pause(1000)
  console.log('fatfish') // 1s later
}
fn()