BFE.dev #34. `Promise.any()` 구현

BFE.dev is like a LeetCode for Front End developers. I’m using it to practice my skills.

분석

Promise.any() takes an iterable of Promise objects and, as soon as one of the promises in the iterable fulfils, returns a single promise that resolves with the value from that promise
e item one by one randomly from rest possible positions.

코드를 보여주세요

/**
 * @param {Array<Promise>} promises
 * @returns {Promise}
 */
function any(promises) {
  // return a Promise, which resolves as soon as one promise resolves
  return new Promise((resolve, reject) => {
    let isFulfilled = false
    const errors = []
    let errorCount = 0
    promises.forEach((promise, index) => promise.then((data) => {
      if (!isFulfilled) {
        resolve(data)
        isFulfilled = true
      }
    }, (error) => {
      errors[index] = error
      errorCount += 1

      if (errorCount === promises.length) {
        reject(new AggregateError('none resolved', errors))
      }
    }))
  })
}

합격