Create a directory named models, as a sibling of the views and routes directories.

Then, create a file named Note.js in that directory, and put this code in it:

const _note_key = Symbol('key');
const _note_title = Symbol('title');
const _note_body = Symbol('body');

module.exports = class Note { 
    constructor(key, title, body) { 
        this[_note_key] = key; 
        this[_note_title] = title; 
        this[_note_body] = body; 
    } 

    get key() { return this[_note_key]; }
    get title() { return this[_note_title]; }
    set title(newTitle) { this[_note_title] = newTitle; }
    get body() { return this[_note_body]; }
    set body(newBody) { this[_note_body] = newBody; }
};

This defines a new class, Note, for use within our Notes application. The intent is to hold data related to notes being exchanged between users of our application.