ES6 Fibonacci Sequence

fibonacci.js

// https://es6console.com/j1fcx8bv

const fibonacci = (startNum=0, prevNum, stopAt=88) => {
  let newNum;
  if(typeof(prevNum) === 'undefined') {
    newNum = startNum || 1;
    console.log('start fibonacci...');
    console.log(startNum);
    fibonacci(startNum, newNum, stopAt);
    return;
  } 
  newNum = prevNum + startNum;
  if(newNum > stopAt) {
    console.log('...end fibonacci');
    return;
  }
  console.log(newNum);
  fibonacci(newNum, startNum, stopAt);  
};
fibonacci();