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 }
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
// bad let arr = [1, 3, 5, 7] function isHasNum (n) { for (let i = 0; i < arr.length; i ++) { if (arr[i] === n) { return true } } return false } // good let arr = [1, 3, 5, 7] let isHasNum = n => arr.some(num => num === n) // best let 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
// 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]
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 } // 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']
巧用解构简化代码
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 }
有的后端返回的键名特别长，你可以这样干
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)
原文：https://mp.weixin.qq.com/s/ql02jlUCl_6mY13XNeGoAA