// 手写 Promiseclass Promise { constructor(executor) { this.status = 'pending' this.value = undefined this.reason = undefined let resolve = value => { if(this.status === 'pending') { this.status = 'fulfilled' this.value = value } } let reject = reason => { if(this.status === 'pending') { this.status = 'rejected' this.reason = reason } } try { executor(resolve, reject) } catch (error) { reject(error) } } then(onFulfilled, onRejected) { if(this.status === 'fulfilled') { onFulfilled(this.value) } if(this.status === 'rejected') { onRejected(this.reason) } }}
