//iterator for ...of循环
{
let arr=['hello','world'];
let map=arr[Symbol.iterator]();
console.log(map.next())
console.log(map.next())
console.log(map.next())
}
{
let obj={
start:[1,3,2],
end:[7,9,8],
[Symbol.iterator](){
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)
}
}
{
let arr=['hello','world'];
for(let value of arr){
console.log('value',value)
}
}