fibonacci.js

/**
 * 斐波那契数列
 * of ES6
 */
function fibonacci () {
  let fn1 = 0;
  let fn2 = 1;
  let next = reset => {
    if (reset) {
      fn1 = 0;
      fn2 = 1;
    }
    let current = fn1;
    [fn1, fn2] = [fn2, fn1 + fn2];
    return { value: current, done: false };
  };
  return { next };
}

fibonacci2.js

/**
 * 斐波那契数列
 * of ES7
 */
function* fibonacci2 () {
  let fn1 = 0;
  let fn2 = 1;
  while (true) {
    let current = fn1;
    [fn1, fn2] = [fn2, fn1 + fn2];
    let reset = yield current;
    if (reset) {
      fn1 = 0;
      fn2 = 1;
    }
  }
}

test.js

let f1 = fibonacci();
let f2 = fibonacci2();
console.log(f1.next(), f2.next());
console.log(f1.next(), f2.next());
console.log(f1.next(), f2.next());
console.log(f1.next(), f2.next());
console.log(f1.next(true), f2.next(true));
console.log(f1.next(), f2.next());
console.log(f1.next(), f2.next());
console.log(f1.next(), f2.next());
console.log(f1.next(), f2.next());