Please, I would like to recover only the key and email from the list, ignoring the other "fields". I wanted to have a list, without loading all the values of all nodes, as I have done lately.
How to achieve this with javascript?
There is no such option. What you can do is just map these fields with a Json just for this purpose, and start recording the records in both the complete structure and the one I'm proposing. This way you will have two structures available for reading / writing.