[Javascript] Convert a forEach method to generator

For example we have a 'forEach' method which can loop though a linked list:

forEach(fn) {
    let node = this.head;
    let counter = 0;
    while (node) {
      fn(node, counter);
      node = node.next;
      counter++;
    }
  }

 

Test:

test('applies a transform to each node', () => {
    const l = new List();

    l.insertLast(1);
    l.insertLast(2);
    l.insertLast(3);
    l.insertLast(4);

    l.forEach(node => {
      node.data += 10;
    });

    expect(l.getAt(0).data).toEqual(11);
    expect(l.getAt(1).data).toEqual(12);
    expect(l.getAt(2).data).toEqual(13);
    expect(l.getAt(3).data).toEqual(14);
  });

 

What if we want to use for...of loop? Then we need to convert LinkedList to support generator partten, the usage of for..of:

test('works with the linked list', () => {
    const l = new List();

    l.insertLast(1);
    l.insertLast(2);
    l.insertLast(3);
    l.insertLast(4);

    for (let node of l) {
      node.data += 10;
    }

    expect(l.getAt(0).data).toEqual(11);
    expect(l.getAt(1).data).toEqual(12);
    expect(l.getAt(2).data).toEqual(13);
    expect(l.getAt(3).data).toEqual(14);
  });

 

Implementation:

*[Symbol.iterator]() {
    let node = this.head;
    while (node) {
      yield node;
      node = node.next;
    }
  }