Matching accented characters with Javascript regexes

Question

Here's a fun snippet I ran into today:

/\ba/.test("a") --> true /\bà/.test("à") --> false 

However,

/à/.test("à") --> true 

Firstly, wtf?

Secondly, if I want to match an accented character at the start of a word, how can I do that? (I'd really like to avoid using over-the-top selectors like /(?:^|\s|'|\(\) ....)

Answer 1

This worked for me:

/^[a-z\u00E0-\u00FC]+$/i 

With help from here

Answer 2

The reason why /\bà/.test("à") doesn't match is because "à" is not a word character. The escape sequence \b matches only between a boundary of word character and a non word character. /\ba/.test("a") matches because "a" is a word character. Because of that, there is a boundary between the beginning of the string (which is not a word character) and the letter "a" which is a word character.

Word characters in JavaScript's regex is defined as [a-zA-Z0-9_].

To match an accented character at the start of a string, just use the ^ character at the beginning of the regex (e.g. /^à/). That character means the beginning of the string (unlike \b which matches at any word boundary within the string). It's most basic and standard regular expression, so it's definitely not over the top.