fibgen.js

'use strict'

function* fibGen(limit) {
  let prevVal = 0, currVal = 1;
  let nextVal = 0;
  while (!limit || currVal <= limit) {
    yield currVal;
    nextVal = currVal + prevVal;
    prevVal = currVal;
    currVal = nextVal;
  }
}

for (let v of fibGen(100)) {
  console.log(v);
}

console.log(Array.from(fibGen(100)));