Promise 串联加载
promise每次执行后,都会返回promise对象.因此可以实现链式调用
(promise D, (promise C, (promise B, (promise A) ) ) )Promise 串联加载
https://blog.fullsize.cn/2021/04/16/notion/promise-chuan-lian-jia-zai/
promise每次执行后,都会返回promise对象.因此可以实现链式调用
(promise D, (promise C, (promise B, (promise A) ) ) )