automatically update new usermeta on vendor registration

Hello,

I want to update some usermeta in wp_usermeta table while vendor registration, I want to assign some unique code for the vendors at the time of registration and store it in wp_usermeta. How can I achieve this, how do I update the field, I do not want to add custom field on the vendor registration form. Will you please help me.

Thanks & regards
Prasad D.

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