JSFiddle - React, Tailwind, and code Playground

HTML

<div id="result"></div>

JavaScript

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);   
}