承诺无法解决这一点

Question

这个简化的代码：

class A {
  constructor() {
    this.promise = new Promise(async resolve => {
      this.resolve = resolve
    })
  }
  then() {
    this.promise.then(...arguments)
    this.resolve(this)
  }
}
const x = new A()
x.then(res => {
  console.log(res)
})

无法解决。

如果将this.resolve(this)更改为this.resolve('done')，则可以使用。有什么想法？

Answer 1

返回的项目( this(具有.then方法，而Promise Resolver(resolve(看到您认为您是用承诺称呼的，因此它试图解决该承诺也：

class A {
  constructor() {
    this.promise = new Promise(async resolve => {
      this.resolve = resolve
      await setTimeout(() => {
        this.x = 1
      }, 1000)
    })
  }
  then() {
    this.promise.then(...arguments)
    this.fin()
    console.log('then running');
  }
  fin() {
    this.resolve(this)
  }
}
const x = new A()
x.then(res => {
  console.log(res)
})

一种可能的解决方案是使用 wraps this的对象调用 resolve，以使解析器函数看不到 .then方法并尝试将其解开：

class A {
  constructor() {
    this.promise = new Promise(async resolve => {
      this.resolve = resolve
      await setTimeout(() => {
        this.x = 1
      }, 1000)
    })
  }
  then() {
    this.promise.then(...arguments)
    return this.fin();
  }
  fin() {
    this.resolve({ result: this })
  }
}
const x = new A()
x.then(res => {
  console.log(res.result)
})