Js How To Reject Wrapper Promise From Inside One?

how to reject wrapper promise from inside one or? in other words, how to make number '3' never printed? Current output: 1 2 3 Expected output: 1 2 new Promise(function(resolve, r

Solution 1:

It looks like you're just missing a return

newPromise(function(resolve, reject) {
    console.log(1)
    resolve()
  })
  .then(() =>console.log(2))
  .then(() => { // how to reject this one if internal fails?returnnewPromise(function(resolve, reject) {
        reject(newError('Polling failure'));
      })
      .then(() =>console.log(21))
  })
  .then(() =>console.log(3))

Solution 2:

In order to reject a promise chain from a .then() handler, you need to either:

Use throw

Throwing any value will mark the promise as unsuccessful:

const p = newPromise(function(resolve, reject) {
  console.log(1)
  resolve()
})
.then(() =>console.log(2))
.then(() => { thrownewError(); })
.then(() =>console.log(3));


p
  .then(() =>console.log("sucessful finish"))
  .catch(() =>console.log("error finish"));

Return a rejected promise

The easiest way is with Promise.reject:

const p = newPromise(function(resolve, reject) {
  console.log(1)
  resolve()
})
.then(() =>console.log(2))
.then(() =>Promise.reject("problem"))
.then(() =>console.log(3));


p
  .then(() =>console.log("sucessful finish"))
  .catch(() =>console.log("error finish"));