可取消的 Promise

原文链接

const makeCancelable = (promise) => {
  let hasCanceled_ = false;
  const wrappedPromise = new Promise((resolve, reject) => {
    promise.then((val) =>
      hasCanceled_ ? reject({isCanceled: true}) : resolve(val)
    );
    promise.catch((error) =>
      hasCanceled_ ? reject({isCanceled: true}) : reject(error)
    );
  });
  return {
    promise: wrappedPromise,
    cancel() {
      hasCanceled_ = true;
    },
  };
}; 

const somePromise = new Promise(r => setTimeout(r, 1000));//创建一个异步操作
const cancelable = makeCancelable(somePromise);//为异步操作添加可取消的功能
cancelable
  .promise
  .then(() => console.log('resolved'))
  .catch(({isCanceled, ...error}) => console.log('isCanceled', isCanceled));
// 取消异步操作
cancelable.cancel();