How to make an iterator out of an ES6 class

Question

How would I make an iterator out of an ES6 class in the same manner as JS1.7 SomeClass.prototype.__iterator__ = function() {...} syntax?

[EDIT 16:00]

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Answer 1

Here's an example for iterating over a 2d matrix custom class in ES6

class Matrix {
    constructor() {
        this.matrix = [[1, 2, 9],
                       [5, 3, 8],
                       [4, 6, 7]];
    }

    *[Symbol.iterator]() {
        for (let row of this.matrix) {
            for (let cell of row) {
                yield cell;
            }
        }
    }
}

The usage of such a class would be

let matrix = new Matrix();

for (let cell of matrix) {
    console.log(cell)
}

Which would output

1
2
9
5
3
8
4
6
7