fibonacci-async.js

// Copyright 2018 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     <https://www.apache.org/licenses/LICENSE-2.0>
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

"use strict";

async function* fibonacciSequence() {
  for (let a = 0, b = 1;; ) {
    yield a;
    const c = a + b;
    a = b;
    b = c;
  }
}

module.exports = async function fibonacci(id, n) {
  for await (const value of fibonacciSequence()) {
    if (n-- === 0) return value;
  }
}