js简写整理

0.给身份证加* 号 

   let idNo = '5123456789789789789'   //身份证号码
        let manySpace=function(num,space){      //生成指定字符和个数的字符串
            let str = ''
            for(let i=0;i<num;i++){
                str+=space
            }
            return str
        }
        console.log(idNo.replace(/(\w{6})\w*(\w{4})/, `$1${manySpace(idNo.length-10,'*')}$2`));   // 结果51234********9789

 

1.通过条件判断给变量赋值布尔值的正确姿势

// bad
if (a === 'a') {
    b = true
} else {
    b = false
}

// good
b = a === 'a'

2.在if中判断数组长度不为零的正确姿势

// bad
if (arr.length !== 0) {
    // todo
}

// good
if (arr.length) {
    // todo
}

3.同理，在if中判断数组长度为零的正确姿势

// bad
if (arr.length === 0) {
    // todo
}

// good
if (!arr.length) {
    // todo
}

4.简单的if判断使用三元表达式

// bad
if (a === 'a') {
    b = a
} else {
    b = c
}

// good
b = a === 'a' ? a : c

5.使用includes简化if判断

// bad
if (a === 1 || a === 2 || a === 3 || a === 4) {
    // todo
}

// good
let arr = [1, 2, 3, 4]
if (arr.includes(a)) {
    // todo
}

 

6.使用some方法判断是否有满足条件的元素

// bad
for (let i = 0; i < arr.length; i ++) {
    // todo
    arr[i].key = balabala
}

// good
arr.forEach(item => {
    // todo
    item.key = balabala
})

 

7.使用forEach方法遍历数组，不形成新数组

// bad
for (let i = 0; i < arr.length; i ++) {
    // todo
    arr[i].key = balabala
}

// good
arr.forEach(item => {
    // todo
    item.key = balabala
})

 

8.使用filter方法过滤原数组，形成新数组

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

// good
let 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

// bad
let arr = [1, 3, 5, 7],
    newArr = []
for (let i = 0; i < arr.length; i ++) {
    newArr.push(arr[i] + 1)
}

// good
let arr = [1, 3, 5, 7]
let newArr = arr.map(n => n + 1) // [2, 4, 6, 8]

 

10.使用Object.values快速获取对象键值

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

// good
let 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
}
// bad
let keys = []
for (value in obj) {
    keys.push(value)
}

// good
let keys = Object.keys(obj) // ['a', 'b']

 

12.解构数组进行变量值的替换

// bad
let a = 1,
    b = 2
let temp = a
a = b
b = temp

// good
let a = 1,
    b = 2
[b, a] = [a, b]

 

13.解构对象

// bad
setForm (person) {
    this.name = person.name
    this.age = person.age 
}

// good
setForm ({name, age}) {
    this.name = name
    this.age = age 
}

 

14.解构时重命名简化命名

// bad
setForm (data) {
    this.one = data.aaa_bbb_ccc_ddd
    this.two = data.eee_fff_ggg
}
// good
setForm ({aaa_bbb_ccc_ddd, eee_fff_ggg}) {
    this.one = aaa_bbb_ccc_ddd
    this.two = eee_fff_ggg
}

// best
setForm ({aaa_bbb_ccc_ddd: one, eee_fff_ggg: two}) {
    this.one = one
    this.two = two
}

 

15.解构时设置默认值

// bad
setForm ({name, age}) {
    if (!age) age = 16
    this.name = name
    this.age = age 
}

// good
setForm ({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
}
// bad
function sayHi (obj) {
    console.log('大家好，我叫' + person.name = '，我今年' + person.age + '了')
}

// good
function sayHi (person) {
    console.log(`大家好，我叫${person.name}，我今年${person.age}了`)
}

// best
function 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]
// bad
function findStudentByAge (arr, age) {
    return arr.filter(function (num) {
        return num === age
    })
}

// good
let findStudentByAge = (arr, age)=> arr.filter(num => num === age)

 

20.函数参数校验

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

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

 转载来自https://juejin.cn/post/6903325147420164104