jQuery function return value

[*PsyKE1*]

I am very new to this, I made this function:

function getID(user){
    $.getJSON('https://twitter.com/users/'+user+'.json?callback=?',
    function(data)
    {
        $('#userid').html(data.id_str);
    });
}

Works well, but I want that instead of modifying the value of #userid I return a value, I tried this:

function getID(user){
    $.getJSON('https://twitter.com/users/'+user+'.json?callback=?',
    function(data)
    {
        return data.id_str;
    });
}

But it makes me return to the function within which it is, not getID.
Solutions?

Thanks!