第一次ES6
// let school = 'magedu'
// console.log(school.charAt(2))// g
// console.log(school[2])// g
// console.log(school.toUpperCase())// MAGEDU
// console.log(school.concat('.com'))//连接
// console.log(school.slice(3))//切片，支持负索引
// console.log(school.slice(3, 5))
// console.log(school.slice(-2, -1))
// console.log(school.slice(-2))
// let url = "www.magedu.com"
// console.log(url.split('.'))
// console.log(url.substr(7, 2))//返回子串从何处开始，取多长
// console.log(url.substring(7, 10))//返回子串，从何处开始，到什么为止
// let s = 'magedu.edu'
// console.log(s.indexOf('ed'))// 3
// console.log(s.indexOf('ed', 4))// 7
// console.log(s.replace('.edu', '.com'))
// s = ' \tmag edu \r\n'
// console.log(s.trim())//去除两端的空白字符。trimLeft、trimRight是非标函数，不要用
// let a='tom'
// // var b=" hello \" "
// var b=18
// // console.log(b)
// c=`my name is ${a} my age is ${b}`
// console.log(c)
// str="hello world12!!";
// console.log(str)
// console.log(a)
// var a
// console.log(a)
/*
a=200;
var b=300;let c=123;
console.log(a)
console.log(b)
console.log(c)
const d=12;
// d=223;
console.log(d)
*/
/*
var a=112;
function hello(){
// var a=12
a=12
console.log(a)
}
console.log(a)
// console.log(hello(a))
hello()
*/
// 类型转换
//弱类型
// console.log('=====string=====')
// console.log(a = 3 + 'magedu', typeof (a))
// console.log(a = null + 'magedu', typeof (a))
// console.log(a = undefined + 'magedu', typeof (a))
// console.log(a = true + 'magedu', typeof (a))
//数字
// console.log('=====number=====')
// console.log(a = null + 8, typeof (a))
// console.log(a = undefined + 8, typeof (a))//undefined没法转换成一个对应的数字
// console.log(a = true + 8, typeof (a))//1
// console.log(a = false + 8, typeof (a))
//boolean
console.log('=====bool=====')
// console.log(a = null + true, typeof (a))
// console.log(a = null + false, typeof (a))
// console.log(a = undefined + true, typeof (a))//unde
// console.log(a = undefined + true, typeof (a))//undefined没法转换成一个对应的数字
// console.log(a = undefined + false, typeof (a))//1
// console.log(a = null & true, typeof (a))
// console.log(a = undefined & true, typeof (a))
// //短路
// console.log(a = null && true, typeof (a))//逻辑运算符，null直接就是false短路
// console.log(a = false && null, typeof (a))//逻辑运算符，false短路返回false
// console.log(a = false && 'magedu', typeof (a))//boolean
// console.log(a = true && 'magedu', typeof (a))//字符串
// console.log(a = true && '', typeof (a))//字符串
// // null
// console.log('=====null=====')
// console.log(a = null + undefined, typeof (a))
let trees = new Array("redwood", "bay", "cedar", "oak", "maple");
console.log(0 in trees);// returns true，0在数组对象的index中
console.log(3 in trees);// returns true，3在数组对象的index中
console.log(6 in trees);// returns false，6不在数组对象的index中
console.log("bay" in trees);// return false，bay不是属性，它是值
console.log("length" in trees);// returns true，length是对象的属性
console.log('~~~~~~~~~~~~~~~~~~~~')
delete trees[3];
console.log(3 in trees);// return false
for (var i = 0; i < trees.length; i++)
console.log(trees[i]);
console.log('~~~~~~~~~~~~~~~~~~~~')
// Custom objects
let mycar = {
color: "red",
model:'Accord',
year: 1998
};
console.log("color" in mycar);// returns true
console.log("model" in mycar);// returns false
console.log('year' in mycar)// true
// x = 42;
// var y = 43;
// let z = 60;
// myobj = new Number();
// myobj.h = 4;// create property h
// console.log(delete x);// returns true (can delete if declared implicitly)
// console.log(delete y);// returns false (cannot delete if declared with var)
// console.log(delete z);// returns false
// console.log(delete Math.PI);// returns false (cannot delete predefined properties)
// console.log(delete myobj.h);// returns true (can delete user-defined properties)
// console.log(delete myobj);// returns true (can delete if declared implicitly)
// console.log('~~~~~~~~~~~~~~~~~~~~')
// var trees = new Array("redwood", "bay", "cedar", "oak", "maple");
// for (var i = 0; i < trees.length; i++)
// console.log(trees[i])
// console.log('==================')
// delete trees[3];//数组中元素被删除，但空着的位置是undefined
// for (var i = 0; i < trees.length; i++)
// console.log(trees[i])
// b=new String('abc')
// console.log(b instanceof String);
// a=new Number(1)
// console.log(a instanceof Number);
// console.log(typeof(a))
// console.log(typeof(100))
// console.log(typeof(typeof(100)))
// if(typeof('abc')=="string"){
// console.log(true)
// }
// console.log(Number.parseInt('1100'));
// let i = 0
// let a = i++
// console.log(a, i)//打印什么0 1
// console.log(a, i++)//打印什么0 1
// a = ++i
// console.log(a, i)//打印什么3 3
// i = 0;
// let a = ++i + i++ + i++ + i;
// console.log(a);//答
//++i + i++ + i++ + i
//1 + 1 + 2 + 3
// 2 3
//2*3 + 3/4 + 4*5
// console.log(1,100 > '200')// false
// console.log(2,300 > '200')// true
// console.log(3,300 > '2000')// false
// console.log(4,3000 > '2a')// false
// console.log(41,3000>NaN) //false
// console.log(5,'3000' > '2000')// true
// //宽松比较
// console.log(6,300 == '300')// true
// console.log(7,'200' == '200')// true
// //严格比较 ===
// console.log(8,300 === '300')// false
// console.log(9,'200' === '200')// true
// console.log(('3' > 30) ? '真' : '假')
// let a=4,b=5,c=1>2?'true':'false'
// console.log(a,b,c)
function hello() {
let a = 1;
var b = 2;
c = 3
}
//let d = 100
if (1) {
let d = 4;
var e = 5;
f = 6
if (true) {
console.log(d)
console.log(e)
console.log(f)
console.log('-------------')
g = 10
var h = 11
}
}
//console.log(a) // 不可见
// console.log(b) //不可见
// console.log(c) //不可见？
//console.log(d) //块作用域使用let，不可见;但是块外的d可见
// console.log(e)//块作用域使用var，可见
// console.log(f)//块作用域隐式声明，可见
// console.log(g)//可见
// console.log(h)//可见
// function * inc(){
// let i=0;
// while (1){
// yield (++i);
// }
// }
// g=inc();
// console.log(g.next().value)
// console.log(g.next())
// console.log(g.next())
// console.log(g.next())
let x = 5
switch (x) {
case 0:
console.log('zero')
break;
case 1:
console.log('one');
case 2:
console.log('two');
case 3:
console.log('three');
break;
case 5:
case 4:
console.log('four');
default:
console.log('other')
break;
}
// a=10
// switch(a){
// case 1:
// case 3:
// case 5:
// console.log('奇数');
// break;
// case 2:
// // console.log('2')
// case 4:
// case 6:
// console.log('偶数');
// break;
// default:
// console.log('null')
// }
arr=[10,20,30,40]
function add(x,y){
return x+y;
}
var obj={
p1:1,
p2:'abc',
p3:[1,2,3],
p4:add
}
for(x=0;x<arr.length;x++){
console.log(x,arr[x]);
}
console.log('------------')
for(x in arr){//index
console.log(x,arr[x])
}
console.log('------------')
for (x in obj){
console.log(x,obj[x])
}
console.log(obj['p4'](3,5))
console.log('------------')
for(x of arr){
console.log(x)
}
for(x of obj){//x 是value
console.log(x)
}
// for (let i = 0; i < 10; i++) {
// console.log(i)
// }
// console.log('~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~')
// for (var x = 0, y = 9; x < 10; x++, y--) {
// console.log(x * y)
// }
// console.log('~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~')
// for (let i = 0; i < 10; i += 3) {
// console.log(i)
// }
// arr=[10,20,30,40]
// for (let x=0;x<arr.length;x++){
// console.log(x,arr[x])
// }
for(let i=1;i<10;i++){
line='';
for(let j=1;j<=i;j++){
line+=`${j}*${i}=${i*j}`;
console.log(line,'|')
}
}
function sum(arr){
for(let x in arr){
console.log(x,typeof(x),arr[x])
}
for(let x of arr){
console.log(x,typeof(x));
}
for(let x=0;x<arr.length;x++){
console.log(x,typeof(x),arr[x])
}
}
sum([3,6,9])
// var add=function _add(a,b){
// console.log(_add)
// console.log(add)
// return a+b
// };
// var add = function (a, b) {
// console.log(add)
// return a + b
// };
// console.log(_add(3,5))
// console.log(add(3, 5))
// x=10
// var sum=function(x){
// result=0
// while(x){
// console.log(x);
// result+=x
// x--;
// return result
// }
// };
// console.log(sum(10));
// var map = (fn,arr)=>{
// let newarr=[];
// for(i in arr){
// newarr[i]= fn(arr[i]);
// }
// return newarr
// }
// let newarr=map((x)=>{return ++x;},[1,2,3,4])
// console.log(newarr)
// let newarr=map((x)=>++x,[1,2,3,4])
// console.log(newarr)
// let newarr=map(x=>++x,[1,2,3,4])
// let counter=function(){
// let i=0;
// return function inc(){
// return ++i;
// }
// return c
///}
// d=counter()
// console.log(d())
// console.log(d())
// console.log(d())
// console.log(d())
// for(x=1;x<10;x++){
// line='';
// for(y=1;y<=x;y++){
// //res=x*y
// //line+=`${y}*${x}=${res}`;
// line +=`${y}*${x}=${x*y} ` ;
// if(x==y){
// console.log(line,'|');
// }
// }
// }
/*
function b(){
console.log('b func')
};
function a(fn){
console.log('a func');
return fn;
}
func=a(b);
func();
*/
/*
let counter=function ()
{
let i=0;
return ()=>++i;
// return function inc(){
// return ++i;
// }
//return inc;
}
c=counter()
console.log(c());
console.log(c());
console.log(c());
console.log(c());
*/
/*
var map=function _map(fn,arr){
let newarr=[]
for(x in arr){
newarr[i]=fn(arr[i]);
}
return newarr;
}
newarr=map(function (x){return ++x},[1,2,3,4])
*/
var map = (fn, arr)=> {
let newarr = []
for (i in arr) {
newarr[i] = fn(arr[i]);
}
return newarr;
}
//newarr = map( (x)=> { return ++x }, [1, 2, 3, 4]);
//newarr=map((x)=> ++x,[1,2,3,4]);
newarr=map(x=>++x,[1,2,3,4]);
console.log(newarr)
/*
//匿名函数
const add=function(x,y){
return x+y;
};
console.log(add(4,6));
//有名字的函数表达式
const sub=function fn(x,y){
return x-y
};
console.log(sub(5,3))
//console.log(fn(3,2)) //fn只能用在函数内部
//有名字的函数表达式
const sum=function _sum(n){
let result=0;
if (n==1) return 1;
return result+=n+_sum(--n) //_sum只能内部使用
};
console.log(sum(4))
*/
// const add=(x,...args)=>{
// console.log(args);
// console.log(x)
// console.log(arguments)
// }
// arr=[1,2,3,4]
// add(...arr)
// var obj={
// a:'abc'
// }
// console.log(obj.a)
// function A(x){
// console.log('A class')
// this.x=x;
// }
// console.log(typeof(A))
// a=new A(100);
// console.log(a);
//定义类
// function Point(x,y){
// this.x=x;
// this.y=y;
// this.show=()=>console.log(this,this.x,this.y);
// console.log('Point~~~~~~');
// }
class Point{
constructor(x,y){
this.x=x;
this.y=y;
//this.show=function(){ console.log(this.x, this.y) };
//this.show=()=>{console.log(this,this.x,this.y)};
}
show(){
console.log(this,this.x,this.y)
}
}
// console.log(Point)
// p1=new Point(4,5);
// console.log(p1);
// console.log('---------')
class Point3D extends Point{
constructor(x,y,z){
super(x, y);
this.z = z;
//this.show =function(){console.log('show 3D',this.x,this.y,this.z); }
// this.show=()=>{console.log('show 3D',this,this.x,this.y,this.z)}
}
show(){
super.show();
console.log('-----',this.z);
}
static print(){
// console.log('3D Point')
return "3D Point"
}
}
//继承
// function Point3D(x,y,z){
// Point.call(this,x,y);
// this.z=z ;
// console.log('Point3D~~~~~~~~');
// }
console.log(Point3D.print())
// console.log(Point3D)
p2=new Point3D(14,15,16);
// console.log(p2);
// p2.show();
console.log(p2.constructor.print());
// var school={
// name:'magedu',
// getNameFunc:function(){
// console.log('b',this.name);
// console.log('a',this);
// return ()=>{
// console.log(this==global);
// return this.name;
// }
// }
// }
// console.log(school.getNameFunc()(school))
// func=school.getNameFunc() //return new func
// console.log(func())
// console.log(func.apply(school,[1,2,3]))
// console.log('c',school.getNameFunc()());
class School{
constructor(){
this.name='magedu';
this.getNameFunc=()=>{
console.log('b', this.name);
console.log('a', this);
return () => {
console.log(this == global);
return this.name;
}
}
}
}
school=new School();
func=school.getNameFunc()//return new function
console.log(func());
// try{
// throw new Number(1);
// }catch (error){
// console.log(error);
// console.log(typeof(error));
// console.log(error.constructor.name);
// }
// 创建一个类
// class Person {
// // 构造器方法
// constructor(name, age) {
// // 构造器中的this是谁？类的实例对象
// this.name = name
// this.age = age
// }
// // 类中的一般方法
// speak() {
// console.log(`我叫${this.name}`)
// // 一般方法speak方法放在了哪里？
// // 答：类的原型对象上，供实例使用
// // 通过Person实例调用speak时，speak中的this就是Person实例
// }
// }
// // 创建一个Person的实例对象
// const p1 = new Person('张三', 18)
// p1.speak()
// // 创建一个Student类，继承了Person类
// class Student extends Person {
// constructor(name, age, grade) {
// // 调研父类的构造器，注意：必须在最开始
// super(name, age)
// this.grade = grade
// }
// }
// // 创建一个Student类的实例对象
// const s1 = new Student('小张', 18, 3)
// s1.speak()
// function breakfast(dessert,drink,...foods){
// console.log(dessert,drink,...foods)
// }
// breakfast('cake','coffee','apple','orange')
// let fruits=['apple','banana']
// foods=['cake',...fruits]
// console.log(fruits)
// console.log(...fruits)
// console.log(foods)
// undifined
// var a; //如果声明了某个变量，但是未对他赋值，则该变量是Undifined类型
// console.log(a)
//null 站一个对象位置
// var obj=new Animal()
// var obj=null
// console.log(2 == true) //false
// console.log(1 + 'hello')//1hello
// console.log('hello' + true)//hellotrue
// console.log(parseInt(3.14));
// console.log(parseInt('3.14a'));
// console.log(parseInt("a3.14")); //NaN,当字符串转换成数字失败时就是NaN,属于Number
// console.log(NaN == 0);//false
// console.log(NaN > 0);//false
// console.log(NaN < 0);//false
// console.log(NaN == NaN);//false //NaN数据在表达式中一定结果为false,除了!=
// console.log(NaN!=0) //true
// var i=10;
// var s='hello';
// var b=false;
// var u=undefined;
// var n=null;
// var obj=new Object();
// console.log(typeof (i))//number
// console.log(typeof (s))//string
// console.log(typeof (b))//boolean
// console.log(typeof (u))//undefined
// console.log(typeof (n))//object
// console.log(typeof (obj))//object
/**
var beyond={
formedIn:'1983',
foundedIn:'香港',
artist:['黄家驹','黄家强','黄贯中','叶士龙']
}
// beyond.formedIn='1983';
// beyond['foundIn']='香港'
// console.log(beyond)
beyond.showArtist=function (){
for(var i=0;i<this.artist.length;i++){
console.log(this.artist[i])
}
}
beyond.showArtist();
var property;
for (property in beyond){
console.log(beyond[property]);
}
*/
/**
showMessage=function (e){
alert(e)
}
showMessage('Hello!!')
*/
/**
var i=0
while(i<10){
i++;
if(i%2===0){
continue;
}
console.log(i);
}
*/
// 28.在文档中创建并插入新的节点.mp4
//29.insertBefore - 在指定的位置插入节点.mp4
// 33.addEventListener - 为对象绑定事件.mp4
/*
var trackCD1=[]
typeof(trackCD1)
trackCD1=['长城','农民','不可一世']
// console.log(trackCD1)//[ '长城', '农民', '不可一世' ]
// console.log(trackCD1.length)//3
// console.log(trackCD1[0])//长城
// console.log(trackCD1[1])//农民
trackCD1[3]='Bye-Bye'
// console.log(trackCD1)//[ '长城', '农民', '不可一世', 'Bye-Bye' ]
trackCD1.push('遥望','温暖的家乡')
//console.log(trackCD1)//[ '长城', '农民', '不可一世', 'Bye-Bye', '遥望', '温暖的家乡' ]
console.log(trackCD1.pop())//温暖的家乡
//console.log(trackCD1)//[ '长城', '农民', '不可一世', 'Bye-Bye', '遥望' ]
console.log(trackCD1.shift())//长城
delete trackCD1[3]
//console.log(trackCD1)//[ '农民', '不可一世', 'Bye-Bye', <1 empty item> ]
console.log(trackCD1.splice(3)) //[ <1 empty item> ]
console.log(trackCD1)//[ '农民', '不可一世', 'Bye-Bye' ]
var trackCD2=['可否冲破','快乐王国']
var tracks=trackCD1.concat(trackCD2)
console.log(tracks)//[ '农民', '不可一世', 'Bye-Bye', '可否冲破', '快乐王国' ]
*/
/*
var weight=160;
var weightIncrease="2.5斤"
a=weight+weightIncrease
console.log(a)
console.log(parseFloat(weightIncrease))
console.log(parseInt(weightIncrease))
b=weight+parseFloat(weightIncrease)
console.log(b)
*/
/**
var beyond={
formedIn:'1983',
foundedIn:'香港',
artist:['黄家驹','黄家强','黄贯中','叶世荣']
}
beyond.showArtist=function(){
for(var i=0;i<this.artist.length;i++){
console.log(this.artist[i])
document.writeln(this.artist[i])
}
}
beyond.showArtist()
console.log(beyond)
*/
/**
var arr=[
{name:'小丽',age:18},
{name:'小米',age:20}
];
for (var item of arr){
console.log(item.name,item.age)
}
var obj={
0:'小美',
1:'小丽'
}
for(let key in obj){
console.log(key,obj[key])
}
var arr=['美美','丽丽']
for(let key in arr){
console.log(key,arr[key])
}
for(let val of arr){
console.log(val)
}
*/
// for(let item in obj.items()){
// console.log(item)
// }
/**
var week=['星期天','星期一','星期二','星期三','星期四','星期五','星期六']
// for(var i=0;i<week.length;i++){
// console.log(week[i])
// }
for(let val of week){
console.log(val)
}
// 区别主要是for of可以拿到键值,而for in可以拿到键名
ar={a:1,b:2,c:3}
for(let val in ar){
console.log(val)
console.log(ar[val])
}
arr=['a','b','c','d']
for(let val of arr ){
console.log(val)
}
*/
/* weather="下雨"
switch(weather){
case '下雨':
alert('忧郁');
break;
case '晴天':
alert ('心情不错');
break ;
default:
alert('心情糟糕');
break;
}
* /
/**
var weather='下雨' ,temprature=26
if ((weather==='晴天')&&(temprature<=26)){
alert('心情不错')
}else if('下雨'){
alert('忧郁')
}else{
alert('心情糟糕')
}
*/
// var words = '宁浩网是个网站'
// console.log(words.length) //7
// console.log(words.charAt(0)) //宁
// console.log(words.charAt(words.length - 1)) //站
// console.log(words.indexOf('网'))//2
// console.log(words.lastIndexOf('网'))//5
// console.log(words.substring(0, 3))//宁浩网
// console.log(words.replace('宁浩网','Hulu'))
// var words = '宁浩网,是个网站'
// console.log(words) //宁浩网,是个网站
// console.log(words.split(','))//[ '宁浩网', '是个网站' ]
// var newWords=words.split(',')
// console.log(newWords)
// console.log(newWords[0])
// console.log(newWords[1])
// m=new Map()
// m.set(1,'a');
// m.set(2,'b');
// m.set(3,'c');
// console.log(m);
//forEach方法只能遍历，没有返回值
// let t=m.forEach((value,key)=>[key,value])
// console.log(t)
//利用数组的map最终返回新的集合的特性
// t=[...m.values()].map(item=>item+100);
// console.log(t);
// function sum(a,b,c){
// return a+b+c
// }
// console.log(sum(1,6,8))
// function sum(a){
// return(b)=>{
// return(c)=>{
// console.log('c')
// return a+b+c
// }
// }
// }
// console.log(sum(2))
// class Serialization{
// constructor(){
// console.log('Serialization constructor~~~');
// if (typeof (this.stringify) !== 'function') {
// throw new ReferenceError('should define stringify.');
// }
// }
// }
// class Point extends Serialization {
// constructor(x, y){
// console.log('Point Constructor~~~~');
// super();//调用父构造器
// this.x = x;
// this.y = y;
// }
// stringify(){
// return `<Point ${this.x}-${this.y}`
// }
// }
// //s = new Serialization(); // 构造Serialization失败
// p = new Point(4,5); //构造子类对象时，调用父类构造器执行也会失败
// class A extends Object{};
// console.log('b',A)
// const A1=class{
// constructor(x){
// this.x=x;
// }
// }
// console.log(A1)
// console.log(new A1(100).x)
// const B=class extends Object{
// constructor(){
// super();
// console.log('B constructor');
// }
// }
// console.log(B)
// b=new B()
// console.log(b)
// const x=(Sup)=>{
// return class extends Sup{
// constructor(){
// super();
// console.log('d','C constructor');
// }
// };
// }
// const C=Sup=>class extends Sup{
// constructor(){
// super();
// console.log('e','C constructor');
// }
// };
// cls=C(A)
// console.log('a',cls)
// c=new cls();
// console.log('3',c);
// c1=new (C(Object))()
// function sum(...numbers){
// return numbers.reduce((preValue,currentValue)=>{
// return preValue+currentValue
// })
// }
// console.log(sum(1,2,3,4))
// class Person extends Object{
// constructor(name,age,props){
// super(props)
// this.name=name
// this.age=age
// console.log('constructor',this.props)
// }
// }
// person=new Person('tom','16')
// console.log(person)
/*
class Serialization{
constructor(){
console.log('Serialization constructor~~~');
if (typeof (this.stringify) !== 'function') {
throw new ReferenceError('should define stringify.');
}
}
}
// const Serialization=Sup=>class extends Sup{
// constructor(){
// console.log('Serialization constructor~~~')
// super(...args)
// if (typeof (this.stringify) !== 'function') {
// throw new ReferenceError('should define stringify.');
// }
// }
// }
class Point {
constructor(x, y){
console.log('Point Constructor~~~~');
super();//调用父构造器
this.x = x;
this.y = y;
}
}
class Point3D extends Serialization(Point){
constructor(x,y,z){
super(x,y);
this.z=z;
}
stringify(){
return `<Point3D ${this.x},${this.y},${this.z}>`
}
}
let p3d=new Point3D(70,80,90);
console.log(p3d.stringify());
*/
/*let food=new Map()
let fruit={}, cook=function (){},dessert='Egg';
food.set(fruit,'Cake');
food.set(cook,'刀叉');
food.set(dessert,'Tea');
console.log(food)
console.log(food.size);
console.log(food.get(fruit));
console.log(food.get(cook));
food.delete(dessert);
console.log(food.has(dessert));
console.log(food.forEach((value, key) => {
console.log(`${key}--${value}`)
}))
*/
/*
class Person{
constructor(name,birthday){
this.name=name,
this.birthday=birthday
}
intro(){
return `${this.name},${this.birthday}`
}
}
class Chef extends Person{
constructor(name,birthday){
super(name,birthday)
}
intro(){
console.log(this.name,this.birthday)
}
}
let wanghao=new Chef('wanghao','1980-03-20');
wanghao.intro()
*/
/**
class Chef {
constructor(food) {
this.food = food,
this.dash = []
}
get menu() {
return this.dash
}
set menu(dish) {
return this.dash.push(dish)
}
static cook(food) {
console.log(food)
}
}
Chef.cook('Tomato')
*/
/**
class Chef {
constructor(food){
this.food=food
}
/**
let desserts=new Set(['Pisa', 'Cake' ,'蛋挞'])
desserts.add('笑脸');
desserts.add('笑脸')
console.log(desserts)
console.log(desserts.size)
console.log(desserts.has('Cake'))
desserts.delete('Cake')
console.log(desserts)
desserts.forEach(dessert=>{
console.log(dessert)
})
desserts.clear()
console.log(desserts)
*/
/*
class Chef {
constructor(food) {
this.food = food,
this.dash=[]
}
get menu(){
return this.dash
}
set menu(dish){
return this.dash.push(dish)
}
cook() {
console.log(this.food)
}
}
let wanghao = new Chef('Tomato')
console.log(wanghao.menu='佳佳求');
console.log(wanghao.menu='pisa');
console.log(wanghao.menu)
*/
/**
class Chef {
constructor(food){
this.food=food
}
cook(){
console.log(this.food)
}
}
let wanghao=new Chef('Tomato')
wanghao.cook()
*/
/**
let chef=function* (foods) {
for (var i=0;i<foods.length;i++){
yield foods[i]
}
}
let wanghao = chef(['Tomato',"Egg"])
console.log(wanghao.next())
console.log(wanghao.next())
console.log(wanghao.next())
*
*/
/**
function * chef(){
yield 'Tomato',
yield "Egg"
}
let wanghao=chef()
console.log(wanghao.next())
console.log(wanghao.next())
console.log(wanghao.next())
*/
/**
*function chef(foods){
let i=0;
return{
next(){
let done=(i>=foods.length);
let value=!done?foods[i++]:undefined;
return {
value: value,
done: done
}
}
}
}
let wanghao=chef(['Tomato','Egg']);
console.log(wanghao.next());
console.log(wanghao.next());
console.log(wanghao.next());
* @param {*} foods
* @returns
*/
/**
let breakfast={
getDrink(){
return "Tea"
}
}
let dinner={
getDrink(){
return "Coffee"
}
}
let Sunday={
__proto__:breakfast,
getDrink(){
return super.getDrink() + 'Milk'
}
}
console.log(Sunday.getDrink())
*/
/**
let breakfast = {
getDrink() {
return 'Tea';
}
};
let dinner = {
getDrink() {
return 'Beer'
}
};
let sunday={
__proto__:breakfast
}
console.log(sunday.getDrink())
console.log(Object.getPrototypeOf(sunday)===breakfast)
sunday.__proto__=dinner
console.log(Object.getPrototypeOf(sunday)===dinner)
*/
/**
let breakfast={
getDrink(){
return 'Tea';
}
};
let dinner={
getDrink(){
return 'Beer'
}
};
let sunday=Object.create(breakfast);
console.log(sunday.getDrink())
console.log(Object.getPrototypeOf(sunday)===breakfast)
Object.setPrototypeOf(sunday,dinner)
console.log(sunday.getDrink())
*/
/**
let breakfast={}
Object.assign(breakfast,{drink:'Beer'})
console.log(breakfast)
*/
/*
console.log(+0 == -0)//true
console.log(+0 === -0)//true
console.log(NaN == NaN)//false
console.log(Object.is(NaN, NaN))//true
console.log(Object.is(-0, +0))//false
*/
/**
let food={}
let drink='hot drink'
food.dessert='Cake'
food[drink]='Tea'
console.log(food)
let breakfast=function superBreakfast(){
}
console.log(breakfast.name)
*
*/
/**
*
简单来说就是它们两者都可以用于遍历，不过for in遍历的是数组的索引（index），
而for of遍历的是数组元素值（value）
var obj={a:1,b:2,c:3}
for (let key in obj){
console.log(key,obj[key])
}
//a 1 b 2 c 3
const array1=['a','b','c']
for (const val of array1){
console.log(val)
}
//a b c
*/
/*
for in更适合遍历对象，当然也可以遍历数组，但是会存在一些问题，
比如：
index索引为字符串型数字，不能直接进行几何运算
var arr=[1,2,3]
for (let index in arr){
let res=index+1
console.log(res)
}
*/
/***
*
for of遍历的是数组元素值，而且for of遍历的只是数组内的元素，不包括原型属性和索引
var arr=[1,2,3]
arr.a=123
Array.prototype.a=123
for (let value of arr){
console.log(value)
}
//1 2 3
for of适用遍历数/数组对象/字符串/map/set等拥有迭代器对象（iterator）的集合，
但是不能遍历对象，因为没有迭代器对象，但如果想遍历对象的属性，
你可以用for in循环（这也是它的本职工作）或用内建的Object.keys()方法
var myObject={
a:1,
b:2,
c:3
}
for(var key of Object.keys(myObject)){
console.log(key+':'+myObject[key])
}
//a:1 b:2 c:3
*/
// console.log(false&&0)
// console.log(true && 0)
// console.log(0 && true)
// console.log(0 && false)
// console.log(01 && 02)
// console.log(null && true)
// console.log(NaN && true)
// console.log(NaN && null)
// console.log(null && NaN)
// console.log(undefined && true)
// console.log(false && undefined)
// console.log(3<<2)
// console.log(null == undefined) //true
// console.log("NaN" == NaN)//false
// console.log(5 == NaN)//false
// console.log(NaN == NaN)//false
// console.log(NaN != NaN)//true
// console.log(false == 0)//true
// console.log(true == 1)//true
// console.log(true == 2)//false
// console.log(undefined == 0)//false
// console.log(null == 0)//false
// console.log("5" == 5)//true
class List extends React.Component {
constructor (props) {
super (props);
this.state = {
1ist: [1, 2, 3],
activeIndex: -1
}；
activate(index) {
this.setState({ activeIndex: index });
render () {
const { list, activeIndex } = this.state;
const lis = list.map(
(item, index) => {
const cls = index === activeIndex ? 'active': ';
return (
<1i
key={index}
className={cls}
onClick=>{() => this.activate(index)}>
</1i>
);
return (
<ul>{lis}</ul>
);
3
ト
render() {
return (
<div>
<input type="text" ref={input => this.todoInput=input}/>
<button onClick={this.add}>Submit #{this.props.count + 1}</button>
</div>
)
}
}
标签：Code,console,log,return,Visual,let,var,Studio,true From： https://www.cnblogs.com/mengdie1978/p/16750925.html