js小技巧

1.获取浏览器cookie值

const cookie = name => `; ${document.cookie}`.split(`; ${name}=`).pop().split(';').shift();

   cookie('_ga');

   Result: "GA1.2.1929736587.1601974046"

2.将RGB转换为16进制

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

   rgbToHex(0, 51, 255);

   Result: #0033ff`

3.复制到剪切板（使用 navigator.clipboard.writeText 轻松将任何文本复制到剪贴板上）

const copyToClipboard = (text) => navigator.clipboard.writeText(text);

   copyToClipboard("Hello World");

4.检查日期是否有效

const isDateValid = (...val) => !Number.isNaN(new Date(...val).valueOf());

   isDateValid("December 17, 1995 03:24:00");

   Result: true

5.找出一年中的某一天（即给出一个日期，程序给出属于本年的第多少天）

const dayOfYear = (date) =>Math.floor((date - new Date(date.getFullYear(), 0, 0)) / 1000 / 60 / 60 / 24);

   dayOfYear(new Date());

   Result: 272

6.将字符串首字母大写

const capitalize = str => str.charAt(0).toUpperCase() + str.slice(1)

   capitalize("follow for more")

   Result: Follow for more

7.计算两个日期之间相差的天数

const dayDif = (date1, date2) => Math.ceil(Math.abs(date1.getTime() - date2.getTime()) / 86400000)

   dayDif(new Date("2020-10-21"), new Date("2021-10-22"))

   Result: 366

8.清除所有cookie

const clearCookies = document.cookie.split(';').forEach(cookie => document.cookie = cookie.replace(/^ +/, '').replace(/=.\*/, `=;expires=${new Date(0).toUTCString()};path=/`));

9.生成随机16进制

const randomHex = () => `#${Math.floor(Math.random() * 0xffffff).toString(16).padEnd(6, "0")}`;

   console.log(randomHex());

   Result: #92b008

10.数组去重

const removeDuplicates = (arr) => [...new Set(arr)];

   console.log(removeDuplicates([1, 2, 3, 3, 4, 4, 5, 5, 6]));

   Result: [ 1, 2, 3, 4, 5, 6 ]

11.从URL中获取查询参数

const getParameters = (URL) => {

URL = JSON.parse('{"' + decodeURI(URL.split("?")[1]).replace(/"/g, '\\"').replace(/&/g, '","').replace(/=/g, '":"') +'"}');

return JSON.stringify(URL)};

   getParameters(window.location)

   Result: { search : "easy", page : 3 }

12.从日期中获取“时分秒”格式的时间

const timeFromDate = date => date.toTimeString().slice(0, 8);

   console.log(timeFromDate(new Date(2021, 0, 10, 17, 30, 0)));

   Result: "17:30:00"

13.确认奇偶数//通过数据%2来判断并返回布尔类型

const isEven = num => num % 2 === 0;

   console.log(isEven(2));

   Result: True

14、求平值

const average = (...args) => args.reduce((a, b) => a + b) / args.length;

average(1, 2, 3, 4);

   Result: 2.5

15.回到顶部（适用于网页右下角快捷返回功能）

//通过将x、y设置为0来实现const goToTop = () => window.scrollTo(0, 0);

   goToTop();

16.反转字符串

const reverse = str => str.split('').reverse().join('');

   reverse('hello world');

   Result: 'dlrow olleh'

17.检查数组是否为空//通过对数组长度判断来确定是否为空

const isNotEmpty = arr => Array.isArray(arr) && arr.length > 0;

   isNotEmpty([1, 2, 3]);

   Result: true

18.获取用户选定的文本

const getSelectedText = () => window.getSelection().toString();

   getSelectedText();

19.打乱数组

const shuffleArray = (arr) => arr.sort(() => 0.5 - Math.random());

   console.log(shuffleArray([1, 2, 3, 4]));

   Result: [ 1, 4, 3, 2 ]

20、检查用户是否处于暗模式

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

   console.log(isDarkMode)

   Result: True or False