I want to open the "interface rule layer and business rule layer"

In.

My troubles once were: DetectionCodeTo repeat writing, write a small part in the client script, and write a large part on the server. I feel sad when I think of this. Canceling the client also wastes user time, occupies bandwidth, increases server load, and is not easy to implement the "continue" function. Undo the server, because skipping the Client Detection is too simple. Besides, there are some things that can only be detected by the server. Both are reluctant, but it is uncomfortable to think of repetition.
Today, we can see these two terms. They don't solve my problem, but let me open them. In the future, we should consider the two parts: what are the rules of the interface layer, what are the server-side rules. Repeat detection is normal, and there is no shame.