自动完成从AJAX响应中读取自定义JSON

I'm trying to use Autocomplete Widget for my autocomplete function,I receive a response with this form:

[
 {"_id":{"mes":"measure1","name":"hold2"},"number":1},
 {"_id":{"mes":"measure2","name":"hold3"},"number":1}
] 

I'm trying to find a way to display the suggestion when typing in an input using this javascript:jquery code :

$('#q').autocomplete({
    source : function(requete, reponse){ 
    $.ajax({
            url : '/app/test/testsearch/', 
            dataType : 'json', 
            data : {
                queryvar : $('#q').val() 
            },

            success : function(donnee){
                //alert('success');
                reponse($.map(donnee._id, function(objet){
                        return objet.mes + ', ' + objet.name; 
                }));
            }
        });
    }

});

With this code I'm getting when I'm typing some suggestions in the input field(with id q)a success Ajax response but I cant display it,any suggestions? Thanks a lot!!!