regex - Have HTML5's a inputs pattern attribute ignore case

Question

I need to have HTML's input elements pattern ignore the case of the value,
like have if the regex is /[a-z]*/ could I get it to match all uppercase letters too?
(I know I could just do /[a-zA-Z]*/, but that was an example.)

Answer 1

I don't think it is possible.

1. The specification on <input pattern> [1,2] specifies that

   • the pattern uses the ECMAScript (i.e. Javascript) flavor of regex

   • it is compiled "with the global, ignoreCase, and multiline flags disabled"

2. In Javascript, the only way to make a regex ignore case is to set the modifier externally (/.../i). The PCRE syntax (?i) is not supported.

Therefore, the pattern is always case-sensitive and [a-zA-Z]* (i.e. making the regex itself explicitly case insensitive) is the only way to match the pattern in a case-insensitive way.