数组解构
const arr = [100, 200, 300]
let [foo, bar, baz] = arr //100 200 300
let [, , baz] = arr //300
let [foo, ...rest] = arr //100,[200,300]
let [foo] = arr //100
let [foo, bar, baz = 400, more = 123] = arr //100 200
//解构时等号后为默认值
let [foo, bar, baz = 400, more = 123,and] = arr //100 200 300 123 undefined
对象解构
const obj = { name: 'zs', age: 18 }
const { name,age:newAge = '20' } = obj //name值为'zs'，newAge为18，覆盖默认值20
字符串扩展方法
const msg = 'Error: foo is not defined.'
//是否以某个字符串开始
console.log(msg.startsWith('Error')) //true
//是否以某个字符串结尾
console.log(msg.endsWith('.')) //true
//是否包含某个字符串
console.log(msg.includes('foo')) //true
函数参数：默认值与剩余参数
function foo(a=100,...args){
console.log(a,args)
}
foo() //100 []
foo(101,10) //101 [10]
foo(200,300,400) //200 [300,400]
箭头函数
const person = {
name:'tom',
say1:()=>{ console.log(this.name) },
say2:function(){ console.log(this.name) }
}
person.say1() //'' this为window
person.say2() //'tom' this为person
对象字面量增强
const bar = "bar"
const obj = {
name: "tom",
//属性名和变量名相同时可省略变量名
bar,
}
console.log(obj) //{name: "tom", bar: "bar"}
Object.assign
const obj = {a:1,b:2}
const obj1 = Object.assign({},obj)
obj1.a=11
console.log(obj) //{a: 1, b: 2}
console.log(obj1) //{a: 11, b: 2}
Object.is
0 == false // true
0 === false // false
+0 === -0 // true
NaN === NaN //false
Object.is(+0,-0) // false
Object.is(NaN,NaN) // true
Class 类
class Person {
constructor (name, age) {
this.name = name;
this.age = age;
}
sayHi () {
console.log(`hi,my name is ${this.name}`)
}
//类方法，this指向的当前的类
static create (name,age) {
return new Person(name,age)
}
}
const p1 = new Person("tom",18)
//调用类方法直接创建实例对象
const p2 = Person.create("zs",19)
console.log(p1) //Person {name: "tom", age: 18}
console.log(p2) //Person {name: "zs", age: 19}
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//子类
class Student extends Person {
constructor (name,age,number) {
//调用父类构造方法
super(name,age)
this.number = number
}
hello () {
//调用父类函数
super.sayHi()
console.log(`学号是 ${this.number}`)
}
}
const s1 = new Student("tom",18,101)
s1.hello() //hi,my name is tom 学号是101
set数据结构
// 创建数据结构
const s = new Set()
s.add(1).add(2).add(3).add(4).add(2)
console.log(s) //Set(4) {1, 2, 3, 4}
//遍历
s.forEach(i => console.log(i)) //1 2 3 4
for (let i of s) {
console.log(i) //1 2 3 4
}
//获得集合的长度
console.log(s.size) //4
//是否存在某个值
console.log(s.has(4)) //true
//删除某个值
console.log(s.delete(100)) //打印false， s不变
console.log(s.delete(3)) //打印true， Set(3) {1, 2, 4}
//清空集合
s.clear() //Set(0) {}
Map 数据结构
const map = new Map()
const a = { a: 1}
const b = 123
map.set(a,100)
map.set(b,200)
//获取对应的值
console.log(map.get(a)) //100
//map.has() 是否包含某个数据
//map.delete() 删除
// map.clear() 清空
map.forEach((value,key) => {
console.log(key,value) //{a: 1} 100 ； 123 200
})
数组includes方法
const arr = [1,true,NaN,23,'hello']
console.log(arr.indexOf(NaN)) //-1 无法查找NaN的位置
console.log(arr.includes(NaN)) //ture
指数运算
console.log(2 ** 3) //8 （2的3次方）
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