Iterators Fibonacci (ES2015)

iterators-fibonacci.js

let fibonacci = {
    [Symbol.iterator]() {
        let pre = 0, cur = 1
        return {
           next () {
               [ pre, cur ] = [ cur, pre + cur ]
               return { done: false, value: cur }
           }
        }
    },
    getSerie(num) {
      let arrFib = [];
      for (let n of this) {
          if (n > num) break
          arrFib.push(n);
      }
      return arrFib.join(" - ")
    }
}

> fibonacci.getSerie(100) === "1 - 2 - 3 - 5 - 8 - 13 - 21 - 34 - 55 - 89" // true