jQuery function to return HTML

Question

I have a function that I want to return HTML and then use it in a conditional if statement in a wider function.

function adverts(selector, dfp, index, tempURL) {
$(dfp).each(function(){
    var code = $(this).data("dfpcode");
    var position = $(this).data("adposition");
    if(index == position) {
        $.get(tempURL + "/shortcodes.php?shortcode=" + code, function() {

        }).done(function(content){
            return content;
        });
    }
    else {
        return "";
    }
});
}

And I want to use it here

var dfpHTML = adverts(selector, ".dfp", i, tempURL).parseHTML();

if(dfpHTML.length > 0) {
    $(div).append(dfpHTML);
}
else {

}

but when I run this in my function this is the error I get TypeError: adverts(...) is undefined