User registration function: Enter the verification code and click "null" to automatically check whether the entered verification code is correct. If the verification code is correct, a green check mark is displayed after the verification code box.

User registration function: Enter the verification code and click "null" to automatically check whether the entered verification code is correct. If the verification code is correct, a green check box is displayed behind the verification code box. after entering the verification code, click an empty box to automatically check whether the entered verification code is correct. If the verification code is correct, a green check mark is displayed after the verification code box.
What is the idea of implementing this function?

Reply to discussion (solution)

The onblur event occurs when the object loses focus.
After the user loses focus, use ajax for verification, and then the front-end displays the result based on the returned data.

After the focus is lost, ajax submits the verification code to the backend for check and returns the result.

In this example, the verification code is not generated. the default verification code is 1234.
Enter the verification code in the input box, and Click Blank to view the result.