How to build a regular expression from a variable

I want to build a REGEXP that matches all results that contain a word, that word is in a variable. This is my code:

function search(buscar){        
    $(".main h2 a").each(function(index) {
        var rege = /^+buscar+$/; //LINE THAT MUST BE CHANGED***
        if(rege.test($(this).text())){
            alert($(this).text());
        }       
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}

var rege = new RegExp('^' + buscar + '$');

or

var rege = new RegExp('^' + buscar.replace(/([.?*+^$[\]\\(){}-])/g, '$1') + '$');

if there's any chance of regex metacharacters being passed in buscar, and you don't want them acting as such.

Of course, it's worth noting that, if there are no regex metacharacters in buscar or we escape them, we're constructing a regex that performs exactly the same test as the == operator.

There's nothing jQuery about this line, incidentally; it's vanilla JavaScript.

var rege = /\bbuscar\b/;

Word boundaries