标签：还需要 new 结束 引号 efault 默认 fun timeout 抛出异常
let name = "SPC"
let ele = `<ul class="star">
<li>张碧晨</li>
<li>江疏影</li>
<li>林允儿</li>
<li>${name}</li>
</ul>`
console.log(ele)
const STUDENTS = ["小明", "小红", "小李"] let [ming, hong, li] = STUDENTS console.log(ming, hong)
const Dog = { name: "旺财", age: 6, play: function () { console.log("play football") } } let {name, age, play} = Dog console.log(name, age) play()
let name = "SPC" let age = 18 let person = { name, age, tip(){ return "这是一个简化的写法" } }
fn = () => {}
let add = (num) => { return num + num } console.log(add(1))
let add = num => num + num
console.log(add(1))
跟大多数语言一样，形参可以有默认值。
function person(name, age, gender="male") { console.log(name) console.log(age) console.log(gender) } person("kidd", 18)
还可以与解构赋值一起使用。
function person({name, age, gender}) { console.log(name) console.log(age) console.log(gender) } const info = { name: "kidd", age: 18, gender:"male" } person(info)
function student(...args) { console.log(args.length) // 4 console.log(args) // ["小明", "小红", "小军", "小李"] } student(...["小明", "小红", "小军"], "小李")
function * gen() { // 函数后加*,表示创建生成器 yield "Hello js" yield "Hello world" } let generator = gen() for(let g of generator){ console.log(g) }
当然生成器也可以进行传参，而且还可以给yield传参数。
function * gen(...arg) { console.log(arg) let first = yield "1" console.log(first) let second = yield "2" console.log(second) } let iter = gen(...["Hello Js", "Hello World"]) console.log(iter.next("A").value) // 如果第一次就给的next()传值，不会有任何效果，因为它并不知道把值传给那个yield console.log(iter.next("B").value) console.log(iter.next("C").value)
可迭代对象，可以使用 for of 进行遍历。 for of 是直接遍历后的值，for in 返回的是索引。
let songs = ["勿忘心安", "最初的梦想", "你曾是少年"] for (let song of songs){ console.log(song) }
如果你不想一次性的遍历完，你可使用 next() 。生成器本身也是迭代器所以自带next ()
let songs = ["勿忘心安", "最初的梦想", "你曾是少年"] let iter = songs[Symbol.iterator]() // 生成器对象 console.log(iter.next()) // 勿忘心安 console.log(iter.next()) // 最初的梦想 console.log(iter.next()) // 你曾是少年 console.log(iter.next()) // undefined
let p = new Promise((resolve, reject) => { setTimeout(function () { let random = Math.floor(Math.random() * 2) if (random){ let data = "数据读取成功" resolve(data) // 该方法表示成功 }else { let data = "数据读取失败" reject(data) // 该方法表示失败 } }, 2000) }) p.then(value => { // value 成功后的结果 console.log(value) }, reason => { // reason 失败后的通知 console.error(reason) })
const p = new Promise((resolve, reject) => { resolve("第一次成功") }) // 因为没写失败，then 也可以不接受失败值 let result = p.then(value => { console.log(value) return new Promise((resolve, reject) => { resolve("第二次成功") }) }).then(value => { console.log(value) return new Promise((resolve, reject) => { reject("出错了！") }) }).then(value => {}, reason => { throw reason// 抛出异常 }) console.log(result) // 最终导致失败
let studentID = new Set([1, 2, 3, 1]) for (let i of studentID){ console.log(i) }
let studentID = new Set([1, 2, 3, 1]) studentID.size // 数量 studentID.has(2) // 该值是否存在集合中 studentID.add(4) // 添加(只能单个加) studentID.delete(4) // 删除(只能单个删除) studentID.clear() // 清空集合 console.log(studentID)
let arr1 = new Set([1,2,3,3]) let arr2 = new Set([3,4,5,5]) // 交集 var result1 = [...arr1].filter(value => arr2.has(value)) console.log(result1) // [3] // 并集 var result2 = [...new Set([...arr1, ...arr2])] console.log(result2) // [1, 2, 3, 4, 5] // 差集 var result3 = [...arr1].filter(value => !arr2.has(value)) console.log(result3) // [1, 2]
class Phone{ // 在 constructor 中写初始化 constructor(brand, price) { this.brand = brand this.price = price } // 必须使用该语法 introduce(){ console.log(`品牌：${this.brand} 价格：${this.price}`) } } XiaoMi = new Phone("小米", 3999) XiaoMi.introduce()
静态方法属于类，而不属于实例化对象。
class Phone{ static brand = "小米" } XiaoMi = new Phone() console.log(XiaoMi.brand) // undefined console.log(Phone.brand) // 小米
ES5
function Phone(brand, price) { this.brand = brand this.price =price } Phone.prototype.call = function () { console.log("我可以打电话了！") } function smartPhone(brand, price, color) { this.color = color Phone.call(this, brand, price) } smartPhone.prototype = new Phone smartPhone.prototype.play = function () { console.log("我可以玩游戏了") } xiaomi = new smartPhone("小米", 3999, "黑色") console.log(xiaomi) xiaomi.call() xiaomi.play()
ES6
class Phone{ constructor(brand, price){ this.brand = brand this.price = price } call(){ console.log("我可以打电话了！") } } class SmartPhone extends Phone{ constructor(brand, price, color) { super(brand, price); this.color = color } play(){ console.log("我可以玩游戏了！") } } xiaomi = new SmartPhone("小米", 3999, "黑色") console.log(xiaomi) xiaomi.call() xiaomi.play()
class Phone{ set price(newVal){ if (typeof newVal == "number"){ console.log("价格被写入了") } } get price(){ console.log("价格被读取了") } } phone = new Phone() phone.price = 3999 phone.price
// 1. 进制 let b = 0b1010 // 二进制 let o = 0o10 // 八进制 let d = 100 // 十进制 let x = 0xff // 十六进制 // 2. 判断 let num = 123 Number.isFinite(num) // 是否有限 Number.isInteger(num) // 是否为整数 Number.isNaN(num) // 是否为 NaN // 3. 字符串转整数或浮点，你可以不使用 Number 进行调用 let str = "3.14圆周率" Number.parseInt(str) Number.parseFloat(str) // 4. 将小数部分抹掉 let float = 3.14 Math.trunc(float) // 5. 给一个数做标记。如果该数大于0，则返回1。如果该数小于0，则返回-1。如果该数等于0，则返回0。 let sign = 200 Math.sign(sign)
// 1. 判断两个值是否完全相等 Object.is(123, 456) // false, 相当于 === // 2. 对象的合并 let config1 = { host: "localhost", port: 3306, user: "root", password: "root", } let config2 = { user: "peng", password: "peng", } Object.assign(config1, config2)
demo.js
export let name = "SPC" export let age = 18 export function Person(name, age) { console.log(`${name}，今年${age}岁了。`) }
html.js
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>导入</title> </head> <body> <script type="module"> import * as demo from "./demo.js" let person = demo.Person(demo.name, demo.age) </script> </body> </html>
分别暴露
export let name = "SPC" export let age = 18 export function Person(name, age) { console.log(`${name}，今年${age}岁了。`) }
统一暴露
let name = "SPC" let age = 18 function Person(name, age) { console.log(`${name}，今年${age}岁了。`) } export { name, age, Person }
默认暴露
let name = "SPC" let age = 18 export default { name: "SPC", age: 18, Person: function (name, age) { console.log(`${name}，今年${age}岁了。`) } }
<script type="module"> // 通用写法 import * as demo from "./demo.js" console.log(demo.name, demo.age) // 解构赋值写法 import {name as name1, age} from "./demo.js" console.log(name1, age) </script>
标签：还需要 new 结束 引号 efault 默认 fun timeout 抛出异常
原文地址：https://www.cnblogs.com/py-peng/p/13544367.html
