You can pass the fields argument as an Array. Then in your read function do something like
function retrieveUserData(user, fields) {
// imagine fields is ['field', 'subfield1']
var fieldVariable = this.users[user] for (f = 0; f < fields.length; ++f) { fieldVariable = fieldVariable[fields[f]]; }
// in this line fieldVariable will point to this.users[user]['field']['subfield1']
return fieldVariable; }
Hope it helps!