Javascript RegExp + Word boundaries + unicode char

Question

I am building search and I am going to use javascript autocomplete with it. I am from Finland (finnish language) so I have to deal with some special characters like ä, ö and å

When user types text in to the search input field I try to match the text to data.

Here is simple example that is not working correctly if user types for example "ää". Same thing with "äl"

var title = "this is simple string with finnish word tämä on ääkköstesti älkää ihmetelkö";
// Does not work
var searchterm = "äl";

// does not work
//var searchterm = "ää";

// Works
//var searchterm = "wi";

if ( new RegExp("\\b"+searchterm, "gi").test(title) ) {
    $("#result").html("Match: ("+searchterm+"): "+title);
} else {
    $("#result").html("nothing found with term: "+searchterm);   
}

http://jsfiddle.net/7TsxB/

So how can I get those ä,ö and å characters to work with javascript regex?

I think I should use unicode codes but how should I do that? Codes for those characters are: [\u00C4,\u00E4,\u00C5,\u00E5,\u00D6,\u00F6]

=> äÄåÅöÖ

Answer 1

What you are looking for is the Unicode word boundaries standard:

http://unicode.org/reports/tr29/tr29-9.html#Word_Boundaries

There is a JavaScript implementation here (unciodejs.wordbreak.js)

https://github.com/wikimedia/unicodejs

Answer 2

this question is old, but I think I found a better solution for boundary in regular expressions with unicode letters. Using XRegExp you can implement a valid \b boundary expanding this

XRegExp('(?=^|$|[^\\p{L}])')

the result is a 4000+ char long, but it seems to work quite performing.

Some explanation: (?= ) is a zero-length lookahead that looks for a begin or end boundary or a non-letter unicode character. The most important think is the lookahead, because the \b doesn't capture anything: it is simply true or false.