Coding Challenge Practice - Question 34

The task is to implement a race() function that works like Promise.race().

The boilerplate code

function race(promises) {
  // your code here
}

The Promise.race() function returns a promise that resolves or rejects as soon as any of the input promises settle.

To recreate that, a new promise is created and returned

return new Promise((resolve, reject) => {
}

Then, each of the promises is looped through

for(const p of promises) {
}

Using promise.resolve, each of them is converted into a real promise, and then resolved or rejected immediately the first one settles.

Promise.resolve(p).then(resolve, reject)

The final code

function race(promises) {
  return new Promise((resolve, reject) => {
    for(const p of promises) {
      Promise.resolve(p).then(resolve, reject)
    }
  })
}

That's all folks!