yourPrefix([a-zA-Z0-9]+)
Matches any alphabetic/numeric characters after ‘yourPrefix’
For your example data in javascript:
'[BBSHORTCODE_LINK'.match('BBSHORTCODE_([a-zA-Z0-9]+)').pop() //'LINK'
'[BBSHORTCODE_BUTTON'.match('BBSHORTCODE_([a-zA-Z0-9]+)').pop() //'BUTTON'
solved Regex take part of string after another part [closed]