类和对象
基本定义：
class Parent{
constructor(name='lmx'){ //name= 默认值
this.name=name
}
}
let v_parent = new Parent('v');
console.log(v_parent);
//输出Parent {name: "v"}
继承
class Parent{
constructor(name='lmx'){
this.name=name
}
}
class Child extends Parent{
constructor(name=’child’){
super(name); //如果super中没有参数则都按照父类的默认值
}
}
console.log(new Child())
getter和setter
class Parent{
constructor(name='lmx'){
this.name=name
}
}
get longName(){
return ‘mk’+this.name;
}
set longName( val){
this.name = val
}
let v = new Parent();
console.log(v.longName()) //调用get方法
v.longName = ‘hello’ //调用set方法
console.log(v.longName())
静态方法：static定义的是类的方法只有类能调用
class Parent{
constructor(name='lmx'){
this.name=name
}
static tell(){
console.log(‘tell’)
}
Parent.tell()
}
静态属性：
ES6明确规定，Class内部只有静态方法，没有静态属性，但是可以通过 类名.变量 来定义
class Parent{
constructor(name='lmx'){
this.name=name
}
}
Parent.abc=’123’
Promise
Promise.all([ ]).then() 表示把多个Promise实例当做一个Promise实例，当所有Promise实例状态发生改变之后，新的Promise才能发生改变，即当三个loadImg实例都加载完之后才会触发Promise.all方法，才会then，才执行showImg
//所有图片加载完了之后才一起显示
function loadImg(src){
return new Promise((resolve,reject)=>{
let img = document.createElement('img');
img.src= src;
img.onload = function(){ resolve(img) };
img.onerror = function(){ reject(err)}
})
}
function showImg(imgs){
imgs.forEach(item=>{
document.body.appendChild(item)
})
};
Promise.all([
loadImg('http://img02.tooopen.com/images/20150928/tooopen_sy_143912755726.jpg'),
loadImg('http://img06.tooopen.com/images/20160818/tooopen_sy_175866434296.jpg'),
loadImg('http://img06.tooopen.com/images/20160818/tooopen_sy_175833047715.jpg')
]).then(showImg)
Promise.race ([ ]).then() 多个实例中有一个状态率先改变之后，race实例会改变，其他的便忽略不管了
//只要有图片加载出来了就显示
function loadImg(src){
return new Promise((resolve,reject)=>{
let img = document.createElement('img');
img.src= src;
img.onload = function(){ resolve(img) };
img.onerror = function(){ reject(err)}
})
}
function showImg(imgs){
imgs.forEach(item=>{
document.body.appendChild(item)
})
};
Promise.race([
loadImg('http://img02.tooopen.com/images/20150928/tooopen_sy_143912755726.jpg'),
loadImg('http://img06.tooopen.com/images/20160818/tooopen_sy_175866434296.jpg'),
loadImg('http://img06.tooopen.com/images/20160818/tooopen_sy_175833047715.jpg')
]).then(showImg)
Iterator接口
在数组中的应用
let arr = ['hello','world'];
let map = arr[Symbol.iterator]();
console.log(map.next());
console.log(map.next());
console.log(map.next());
//输出，done变为true之后循环截止
自定义iterator接口
for...of循环
let obj = {
start:[3,5,6],
end:[4,8,9],
[Symbol.iterator](){ //iterator小写
let self= this;
let index = 0;
let arr = self.start.concat(self.end);
let len = arr.length;
return{
next(){
if(index<len){
return {
value:arr[index++],
done:false}
}else{
return {
value:arr[index++],
done:true
}
}
}
}
}
} ;
for(let key of obj){
console.log(key)
}