for-defer-of-go.js

const go = {
  [Symbol.iterator]() {
    const funcs = [];
    const defer = func => funcs.push(func);
    let index = 0;
    const flush = () => {
      let func;
      while (func = funcs.pop()) {
        func();
      }
    };
    return {
      next() {
        if (index++ === 0) {
          return {value: defer};
        } else {
          flush();
          return {done: true};
        }
      },
      return: flush,
    };
  }
};

for (const defer of go) {
  console.log(0);
  defer(() => console.log(4));
  console.log(1);
  defer(() => console.log(3));
  console.log(2);
}

for (const defer of go) {
  console.log(5);
  defer(() => console.log(9));
  console.log(6);
  defer(() => console.log(8));
  console.log(7);
  throw new Error('10');
}