Javascript RegExp + Word boundaries + unicode characters

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There appears to be a problem with Regex and the word boundary \b matching the beginning of a string with a starting character out of the normal 256 byte range.

Instead of using \b, try using (?:^|\\s)

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("(?:^|\\s)"+searchterm, "gi").test(title) ) {
    $("#result").html("Match: ("+searchterm+"): "+title);
} else {
    $("#result").html("nothing found with term: "+searchterm);   
}

Breakdown:

(?: parenthesis () form a capture group in Regex. Parenthesis started with a question mark and colon ?: form a non-capturing group. They just group the terms together

^ the caret symbol matches the beginning of a string

| the bar is the “or” operator.

\s matches whitespace (appears as \\s in the string because we have to escape the backslash)

) closes the group

So instead of using \b, which matches word boundaries and doesn’t work for unicode characters, we use a non-capturing group which matches the beginning of a string OR whitespace.

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