question/implement-promise-all

[giscus[bot]]

question/implement-promise-all

北美前端面试攻略

https://us-fe.github.io/question/implement-promise-all.html

[xiaoyu2er]

/**
 * @param {Array<any>} promises - notice input might have non-Promises
 * @return {Promise<any[]>}
 */
function all(promises) {
  return new Promise((resolve, reject) => {
    let len = promises.length;
    const result = [];
    if (promises.length === 0) {
      resolve(result);
    }
    promises.forEach((p, i) => {

      (p && p.then ? p : Promise.resolve(p))
        .then(val => {
          result[i] = val;
          if (--len === 0) {
            resolve(result);
          }
        })
        .catch(reject);
    })
  });
}


all([Promise.resolve(1), 2])
  .then(r => console.log(r))
  .catch(r => console.log(r));

[xiaoyu2er]

p && p.then ? p : Promise.resolve(p) 可以简单写成 Promise.resolve(p)

[xiaoyu2er]

这个题目本身还是比较简单的
答案

[]
[1,2,3,4]
"error"