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20条JavaScript代码简洁的写法

JavaScript

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 : c5、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 ++) {// todoarr[i].key = balabala}// goodarr.forEach(item => {// todoitem.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.namethis.age = person.age}// goodsetForm ({name, age}) {this.name = namethis.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_dddthis.two = data.eee_fff_ggg}// goodsetForm ({aaa_bbb_ccc_ddd, eee_fff_ggg}) {this.one = aaa_bbb_ccc_dddthis.two = eee_fff_ggg}// bestsetForm ({aaa_bbb_ccc_ddd: one, eee_fff_ggg: two}) {this.one = onethis.two = two}15、解构时设置默认值// badsetForm ({name, age}) {if (!age) age = 16this.name = namethis.age = age }// goodsetForm ({name, age = 16}) {this.name = namethis.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'【20条JavaScript代码简洁的写法】let person = {name: '张三',age: 38,children: {name: '张小三'}}let childrenName = person.children && person.childre.name18、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)



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