SOURCE

function* generator() {
  yield 'hello';
  yield 'world';
  return 'ending';
  yield  'continue';
}
var hw = generator();  //  返回一个遍历器Iterator对象
console.log(hw.next());
console.log(hw.next());
console.log(hw.next());
console.log(hw.next());
console.log(hw.next());
console.log(hw.next());
console.log(hw.next());

// 作用 循环调用