const myBoolean = !! myVariable; 
!!null // false 
!!undefined // false 
!!false // false 
!!ture // ture 
!!"" // false 
!!"string" // true 
!!0 // false 
!!1 // true 
!!{} // true 
!![] // true 

const myObject = {... myProperty && {propName：myPoperty}}; 
let myProperty = 'Jhon' 
const myObject = {...myProperty && {propName: myProperty}}; // {propName: "Jhon"} 
let myProperty = '' 
const myObject = {...myProperty && {propName: myProperty}}; // {} 

const mergedObject = { ...objectOne, ...objectTwo }; 
const mergedObject = { ...{name: 'Jhon', age: '18'}, ...{name1: 'jhon1', age1: '12'}}; 
// {name: "Jhon", age: "18", name1: "jhon1", age1: "12"} 
const mergedObject = { ...{name: 'Jhon', age: '18'}, ...{name: 'jhon1', age:'12'}}; 
// {name: "jhon1", age: "12"} 

[varA，varB] = [varB，varA]; 
let a = 1; 
let b = 2; 
[a, b] = [b, a] // a = 2 b = 1 
5.删除Boolean 为 false 值
const clean = dirty.filter(Boolean); 
const clean = [0, false, true, undefined, null, '', 12, 15].filter(Boolean); 
// [true, 12, 15] 

const stringArray = numberArray.map(String); 
const stringArray = [1, 2, 3].map(String); 
["1", "2", "3"] 

const numberArray = stringArray.map(Number); 
const stringArray = ["1", "2", "3"].map(String); 
// [1, 2, 3] 

const formatted = JSON.stringify(myObj, null, 4); 
const formatted = JSON.stringify({name: 'Jhon', age: 18, address: 'sz'}, null, 4); 
/* 
{ 
 "name": "Jhon", 
 "age": 18, 
 "address": "sz" 
} 
*/ 

const numArray = Array.from(new Array(10), (x, i)=> i); 
// [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] 

const code = Math.floor(Math.random() * 1000000).toString().padStart(6, "0"); 
// 942377 

const IDReg= /(^[1-9]d{5}(18|19|([23]d))d{2}((0[1-9])|(10|11|12))(([0-2][1-9])|10|20|30|31)d{3}[0-9Xx]$)|(^[1-9]d{5}d{2}((0[1-9])|(10|11|12))(([0-2][1-9])|10|20|30|31)d{2}[0-9Xx]$)/; 

const searchObj = search => JSON.parse(`{"${decodeURIComponent(search.substring(1)).replace(/"/g, '\"').replace(/&/g, '","').replace(/=/g, '":"')}"}`); 
// 假如请求url为 
// 'https://www.baidu.com"text-align: center">

12. JS 对象转 url 查询字符串




const objectToQueryString = (obj) => Object.keys(obj).map((key) => `${encodeURIComponent(key)}=${encodeURIComponent(obj[key])}`).join('&'); 
objectToQueryString({name: 'Jhon', age: 18, address: 'beijing'}) 
// name=Jhon&age=18&address=beijing 


13.获取数组交集




const similarity = (arr, values) => arr.filter(v => values.includes(v)); 
similarity([1, 2, 3], [1, 2, 4]); // [1,2] 


14.检测设备类型


使用正则表达式来检测 navigator.userAgent 属性判断设备是在移动设备还是在台式机/笔记本电脑打开。


const detectDeviceType = () =>/Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|OperaMini/i.test(navigator.userAgent) "color: #ff0000">15. 将数字转化为千分位格式




const toDecimalMark = num => num.toLocaleString('en-US'); 
toDecimalMark(12305030388.9087); // "12,305,030,388.909" 


16 多维数组转一维数组




const deepFlatten = arr => [].concat(...arr.map(v => (Array.isArray(v) "color: #ff0000">17.过滤对象数组




const reducedFilter = (data, keys, fn) =>data.filter(fn).map(el =>keys.reduce((acc, key) => {acc[key] =el[key];return acc;}, {})); 
const data = [ 
 { 
 id: 1, 
 name: 'john', 
 age: 24 
 }, 
 { 
 id: 2, 
 name: 'mike', 
 age: 50 
 } 
]; 
let a = reducedFilter(data, ['id', 'name'], item => item.age > 24); // [{ id: 2, name: 'mike'}] 



18.驼峰字字符串格式化


转换驼峰拼写的字符串为特定格式。
使用 String.replace() 去除下划线，连字符和空格，并将驼峰拼写格式的单词转换为全小写。省略第二个参数 separator ，默认使用 _ 分隔符。


const fromCamelCase = (str, separator = '_') =>str.replace(/([a-zd])([A-Z])/g, '$1' + separator + '$2').replace(/([A-Z]+)([A-Z][a-zd]+)/g, '$1' + separator + '$2').toLowerCase(); 
fromCamelCase('someDatabaseFieldName', ' '); // 'some database field name' 
fromCamelCase('someLabelThatNeedsToBeCamelized', '-'); // 'some-label-that-needs-to-be-camelized' 
fromCamelCase('someJavascriptProperty', '_'); // 'some_javascript_property' 


19.是否为绝对地址




const isAbsoluteURL = str => /^[a-z][a-z0-9+.-]*:/.test(str); 
isAbsoluteURL('https://google.com'); // true 
isAbsoluteURL('ftp://www.myserver.net'); // true 
isAbsoluteURL('/foo/bar'); // false 


20.获取两个日期相差天数




const getDaysDiffBetweenDates = (dateInitial, dateFinal) => (dateFinal - dateInitial) / (1000 * 3600 * 24); 
getDaysDiffBetweenDates(new Date('2017-12-13'), new Date('2017-12-22')); // 9 


21.数组去重




const deDupe = (myArray) => [... new Set(myArray)]; 
deDupe([1, 1, 2, 1, 3, 3, 4]) 
// [1, 2, 3, 4] 



22.数组对象去重




const uniqueElementsBy = (arr, fn) =>arr.reduce((acc, v) => {if (!acc.some(x => fn(v, x))) acc.push(v);return acc;}, []); 
uniqueElementsBy([{id: 1, name: 'Jhon'}, {id: 2, name: 'sss'}, {id: 1, name: 'Jhon'}], (a, b) => a.id == b.id) 
// [{id: 1, name: 'Jhon'}, {id: 2, name: 'sss'}] 



23. RGB 颜色转 16进制颜色




const RGBToHex = (r, g, b) => ((r << 16) + (g << 8) + b).toString(16).padStart(6, '0'); 
RGBToHex(255, 165, 1); // 'ffa501' 


24. 常用密码组合正则




const passwordReg = /("color: #ff0000">25. 判断dom元素是否具有某个className




const hasClass = (el, className) => new RegExp(`(^|\s)${className}(\s|$)`).test(el.className); 



以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。

                                
                                

                                    JavaScript常用代码 
                                

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