How can I change the default username to the drop-down menu I need to modify the logon modification of Yii2?

Use the login registration function provided by Yii2: a new site is developed, but the username field in the old table must be used, make it into this style (using the select2javascript plug-in), then how do I use the User component that comes with hack to convert username...

Use the logon registration function provided by Yii2:
Currently, a new site needs to be developed, but the username must be created using the username field in the old table.

This style (using the select2 javascript plug-in), how can I change the username from the User component that comes with hack to the existing data that I need (the existing data has been converted to json )? I feel that the login registration package provided by yii2 is very good. I feel that there is no way to modify it. I hope some experts can give me some answers. Thank you very much.

Reply content:

Use the logon registration function provided by Yii2:
Currently, a new site needs to be developed, but the username must be created using the username field in the old table.

This style (using the select2 javascript plug-in), how can I change the username from the User component that comes with hack to the existing data that I need (the existing data has been converted to json )? I feel that the login registration package provided by yii2 is very good. I feel that there is no way to modify it. I hope some experts can give me some answers. Thank you very much.