A simple range generator in JavaScript for iterating through a left-closed, right-open interval

range.js

function* range(start, end, step) {
  if(end === undefined) {
    end = start;
    start = 0;
  }

  if(step === 0) throw new RangeError('step must be non-zero');
  if(step === undefined) step = Math.sign(end - start);

  const dir = Math.sign(step);
  if(Math.sign(end - start) != dir) {
    const temp = start;
    start = end;
    end = temp;
  }

  for(let i = start; Math.sign(end - i) == dir; i += step) {
    yield i;
  }
}

More examples:

for(const x of range(5, 0)) {
  console.log(x);
}

Console output:

5
4
3
2
1