Multi word case agnostic :contains selector and word highlighter

var multiWord = function(string){ return new RegExp("(" + string.split(" ").join(")|(") + ")",'gi'); }
 
$.expr[":"].contains = $.expr.createPseudo(function(arg) {
    return function( elem ) {
        return multiWord(arg).test($(elem).text());
    };
});
 
function highLight(string, selector) {
    selector = selector || "";
    var re = multiWord(string);
    $(selector + ":contains(" + string + ")").each(function(){
        $(this).html(
            $(this).text().replace(re, function($1){
                return "<em>" + $1 + "</em>";
            })
        );
    });
}