Works in jQuery, React, Angular, Javascript es6 and es5
(^[A-Z]{2}[0-9]{2}\s?[A-Z]{3}$)|(^[A-Z][0-9]{1,3}[A-Z]{3}$)|(^[A-Z]{3}[0-9]{1,3}[A-Z]$)|(^[0-9]{1,4}[A-Z]{1,2}$)|(^[0-9]{1,3}[A-Z]{1,3}$)|(^[A-Z]{1,2}[0-9]{1,4}$)|(^[A-Z]{1,3}[0-9]{1,3}$)
Forked from here but updated to work in JavaScript, and added an optional space