PromiseA 规范

Promise.all 文档
https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Promise/all

Promise A+

Promise 参考资料

https://promisesaplus.com/
http://www.ituring.com.cn/article/66566 Promise A+ 规范
https://segmentfault.com/a/1190000009478377
Promise resolve & reject 需要return吗
https://www.jianshu.com/p/d1ed65ba6f15