20条javaScript 示例代码让你的代码更简洁

1.通过条件判断给变量赋值布尔值的正确姿势

// badif (a === 'a') {    b = true} else {    b = false}// goodb = a === 'a'

2.在if中判断数组长度不为零的正确姿势

// badif (arr.length !== 0) {    // todo}// goodif (arr.length) {    // todo}

3.同理，在if中判断数组长度为零的正确姿势

// badif (arr.length === 0) {    // todo}// goodif (!arr.length) {    // todo}

4.简单的if判断使用三元表达式

// badif (a === 'a') {    b = a} else {    b = c}// goodb = a === 'a'   a : c

5.使用includes简化if判断

// badif (a === 1 || a === 2 || a === 3 || a === 4) {    // todo}// goodlet arr = [1, 2, 3, 4]if (arr.includes(a)) {    // todo}

巧用数组方法，尽量避免用for循环

6.使用some方法判断是否有满足条件的元素

// badlet arr = [1, 3, 5, 7]function isHasNum (n) {    for (let i = 0; i < arr.length; i ++) { if (arr[i] === n) {     return true }    }    return false}// goodlet arr = [1, 3, 5, 7]let isHasNum = n => arr.some(num => num === n)// bestlet arr = [1, 3, 5, 7]let isHasNum = (n, arr) => arr.some(num => num === n)

7.使用forEach方法遍历数组，不形成新数组

// badfor (let i = 0; i < arr.length; i ++) {    // todo    arr[i].key = balabala}// goodarr.forEach(item => {    // todo    item.key = balabala})

8.使用filter方法过滤原数组，形成新数组

// badlet arr = [1, 3, 5, 7],    newArr = []for (let i = 0; i < arr.length; i ++) {    if (arr[i] > 4) { newArr.push(arr[i])    }}// goodlet arr = [1, 3, 5, 7]let newArr = arr.filter(n => n > 4) // [5, 7]

9.使用map对数组中所有元素批量处理，形成新数组

// badlet arr = [1, 3, 5, 7],    newArr = []for (let i = 0; i < arr.length; i ++) {    newArr.push(arr[i] + 1)}// goodlet arr = [1, 3, 5, 7]let newArr = arr.map(n => n + 1) // [2, 4, 6, 8]

巧用对象方法，避免使用for...in

10.使用Object.values快速获取对象键值

let obj = {    a: 1,    b: 2}// badlet values = []for (key in obj) {    values.push(obj[key])}// goodlet values = Object.values(obj) // [1, 2]

11.使用Object.keys快速获取对象键名

let obj = {    a: 1,    b: 2}// badlet keys = []for (value in obj) {    keys.push(value)}// goodlet keys = Object.keys(obj) // ['a', 'b']

巧用解构简化代码

12.解构数组进行变量值的替换

// badlet a = 1,    b = 2let temp = aa = bb = temp// goodlet a = 1,    b = 2[b, a] = [a, b]

13.解构对象

// badsetForm (person) {    this.name = person.name    this.age = person.age }// goodsetForm ({name, age}) {    this.name = name    this.age = age }

14.解构时重命名简化命名

有的后端返回的键名特别长，你可以这样干

// badsetForm (data) {    this.one = data.aaa_bbb_ccc_ddd    this.two = data.eee_fff_ggg}// goodsetForm ({aaa_bbb_ccc_ddd, eee_fff_ggg}) {    this.one = aaa_bbb_ccc_ddd    this.two = eee_fff_ggg}// bestsetForm ({aaa_bbb_ccc_ddd: one, eee_fff_ggg: two}) {    this.one = one    this.two = two}

15.解构时设置默认值

// badsetForm ({name, age}) {    if (!age) age = 16    this.name = name    this.age = age }// goodsetForm ({name, age = 16}) {    this.name = name    this.age = age }

16.||短路符设置默认值

let person = {    name: '张三',    age: 38}let name = person.name || '佚名'

17.&&短路符判断依赖的键是否存在防止报错'xxx of undfined'

let person = {    name: '张三',    age: 38,    children: { name: '张小三'    }}let childrenName = person.children && person.childre.name

18.字符串拼接使用${}

let person = {    name: 'LiMing',    age: 18}// badfunction sayHi (obj) {    console.log('大家好，我叫' + person.name = '，我今年' + person.age + '了')}// goodfunction sayHi (person) {    console.log(`大家好，我叫${person.name}，我今年${person.age}了`)}// bestfunction sayHi ({name, age}) {    console.log(`大家好，我叫${name}，我今年${age}了`)}

19.函数使用箭头函数

let arr [18, 19, 20, 21, 22]// badfunction findStudentByAge (arr, age) {    return arr.filter(function (num) { return num === age    })}// goodlet findStudentByAge = (arr, age)=> arr.filter(num => num === age)

20.函数参数校验

// badlet findStudentByAge = (arr, age) => {    if (!age) throw new Error('参数不能为空')    return arr.filter(num => num === age)}// goodlet checkoutType = () => {    throw new Error('参数不能为空')}let findStudentByAge = (arr, age = checkoutType()) =>    arr.filter(num => num === age)