class List{
constructor(){
this.data = [1,2,3];
}
[Symbol.iterator](){
return this.data;
}
}
let list = new List();
for(let i of list)
console.log(i);
Error in the for() line:
Uncaught TypeError: undefined is not a function
So it's not possible to use iterator with our own classes like in PHP?
This isn't working because you have not properly implemented the iterable protocol. For an object to be an iterable, it must have an @@iterator key (which you have), which returns an iterator, which is what you are missing (arrays are iterables but are not iterators).
However, since an array is an iterable, you can use its @@iterator property to get an iterable for it. Then you can return that instead.
class List{
constructor(){
this.data = [1,2,3];
}
[Symbol.iterator](){
return this.data[Symbol.iterator]();
}
}
let list = new List();
for(let i of list)
console.log(i);You can read more about the Javascript iterable/iterator protocol here.
You can make the the [Symbol.iterator] property of you object a generator rather than a function and just yield the list elements individually with *:
class List {
constructor() {
this.data = [1, 2, 3];
}
*[Symbol.iterator]() {
yield* this.data;
}
}
let list = new List();
for (let i of list) {
console.log(i);
}
return this.data[Symbol.iterator]()*[Symbol.iterator](){ for(let i of this.data) yield i; }