How to use a variable in getElementById (AJAX & PHP) [closed]

The code is a function in AJAX that receives from a PHP page 2 variables: id and nombrediv . nombrediv is the id of the div where I want to show the result of the ajax function, but it does not work.

Can this be done?:

document.getElementById(VARIABLE)

What is the way to write it?

var editarMedidas = function(id, nombrediv) {
    var xhr = new XMLHttpRequest();
    xhr.open("GET", "editar-medidas.php?id=" + id + "&nd=" + nombrediv);
    xhr.onreadystatechange = function() {
        if (xhr.readyState == 4) {
            if(xhr.status == 200) {
                // AQUI ES EL PROBLEMA, SE PUEDE PONER UNA VARIABLE PARA QUE BUSQUE LA DIV CON ESE NOMBRE?                  
                var caja=document.getElementById(nombrediv);     
                caja.innerHTML = xhr.responseText;     
            }        
        }                 
    }
    xhr.send(null); 
}