What is a Cookie problem that needs to be paid attention to in JavaScript ES6 Fetch API?

JavaScript ES6 Fetch API needs to pay attention to what a Cookie problem is, I believe that many inexperienced people do not know what to do, so this paper summarizes the causes of the problem and solutions, through this article I hope you can solve this problem.

When I am doing a test of comparison between Stateful and Stateless BSP application (mentioned in blog Stateless and Stateful-Different behavior in application side), I meet with a strange issue.

The conclusion is stateful BSP application will handle request sequentially. Suppose in client I send two request An and B to server. Request A takes 3 seconds to finish and B 2 seconds.

The request is sent via jQuery API. It means for stateful application, I will observe the following timeline in Chrome network tab:

(1) the start time of both request are almost the same, since I send out two request in client code almost at the same time. (2) even though the second request itself takes 2 seconds to finish, the total processing time for it is 3 seconds waiting for A to finish first + 2 seconds = 5 seconds in the end.

The above test did verify the conclusion. However when I change the approach to send request into ES6 fetch API

Jerry Test Stateful