for in range javascript

1function range(start, end) {
2	/* generate a range : [start, start+1, ..., end-1, end] */
3	var len = end - start + 1;
4	var a = new Array(len);
5	for (let i = 0; i < len; i++) a[i] = start + i;
6	return a;
7}

1function* range(start=0, end=null, step=1) {
2  if (end == null) {
3    end = start;
4    start = 0;
5  }
6
7  for (let i=start; i < end; i+=step) {
8    yield i;
9  }
10}
11