Detailed Jiu Zheng expression Form Validation instance _ regular expression

First look at the effect chart:

First of all, to explain some of the symbolic relevance

* Match the preceding subexpression 0 or more times;
^ matches the start position of the input string; $ matches the end position of the input string
1./^$/This is a common format.
2. Enter the function you want to implement.
\d matches a numeric character, equivalent to [0-9]
+ Match the preceding subexpression one or more times;
？ Matches the preceding subexpression 0 times or once;
The following code to analyze the form to verify the regular expression, the specific code is as follows:

<! DOCTYPE html>  

The above is the form validation regular expression instance code, and I hope it helps.