[jQuery] Synthax problem

[jQuery] Synthax problem


Hi everyone
I have a problem with the use of an ajax call in a function. I want to
get the result of the ajax call for processing to the return of the
function.
I've tried something like that
function checkUsername(s)
{
    TO_RETURN = $.ajax({
        type: "POST",
        url: 'http://'+ CURRENT_DOMAIN + '/ajax/checkUsernameExists/
username/'+s,
        async: false,
        success: function(msg){
            if(msg=='true'){
                return true;
            } else {
                return false;
            }
        }
    });
    if(TO_RETURN) return true;
    else return false;
}
But it didn't work ...
If anyone could help me :)
PS : I'm a novice in jQuery and i have low skills in javascripts