node_js_notes.txt

 - NODE.JS NOTES -

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GENERAL:

    -Node is essentially a JavaScript shell
        -JS can be entered line by line or run by-the-file
            - "node <+file_name.js>"
    -Enter "node" in the terminal to launch it
    -Node servers use an "event-loop" instead of the more common single-thread per-connection
        -allows multiple connections on the same input/output thread
        -works best for situations where events need to be handled quickly in real-time, with minimal processing
            -better suited for a chat app than math calculations
    -Node comes with NPM (Node Package Manager) by default

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NPM (NODE PACKAGE MANAGER):

    -Like pip in Python
    -Used to manage project dependencies
        -these dependencies are .js files and libraries
        -these chunks called "modules" in MEAN / MERN stacks
            -"gems" in Ruby
            -"libraries" in Python
            -called "middleware" generically
        -npm fetches and prepares this "middleware"
    -Can install middleware modules from your computer (locally) or remotely from the npm registry
    -"nodemon" package auto-restarts the JS file or project whenever a save is made
        -still MUST refresh the browser page though!
        -install globally, on every Node project
            -most modules will not be installed globally
        -MUST start server with " nodemon [+server.js_file] " instead of " node [+server.js_file] "!
            -otherwise, Nodemon won't keep the server updated for you

    *************************************************************************************************
    -i.e.   TERMINAL:

            // "-g" option indicates to install nodemon globally
            npm install -g nodemon

            // Mac users may need to use "sudo" to install packages globally
            sudo npm install -g nodemon

            // Can install multiple packages at once!
            npm install express mongoose

        (^ demonstrates how to install a package with npm ^)
        *************************************************************************************************

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SERVER-FOLDER STRUCTURE MODULARIZATION:

    -Best practice to have habit of modularizing projects from the start
        -makes keeping track of content easy as project grows
        -modules can be easily imported/exported between server files this way!
    -Project should be structured based on models
        -because Express is used strictly for hanglind all comms with the database in MERN
    -Basic server-folder structure:
        -"server" folder:
            -holds all server related files
            -holds each of the following:
                1."config" folder:
                    -holds config files?
                2. "controllers" folder:
                    -holds all logic for each model 
                    -i.e. creating, updating etc...
                3. "models" folder:
                    -holds all the model schemas
                4. "routes" folder:
                    -holds all routes for each model
                5. "server.js" file:
                    -handles all server logic with Express!
                6. "packages.json" file:
                    -" npm init -y "

    -Importing/exporting between files:

        1. Exporting:
            -i.e. " module.exports = [+export(s)] "
            -will export whatever?
            -like functions

        *************************************************************************************************
        -i.e.   *MY_MODULE.JS*

                // exports "greet()" function
                module.exports.greet = function() {
                    console.log("Hello! We are exporting a function called greet!");
                };

                // exports "add()" function
                module.exports.add = function(num1, num2) {
                    console.log("The sum is: ", num1, num2);
                };

                // exports the same "greet()" and "add()" functions, but within a single object with names as keys and value as anon-functions
                module.exports = {
                    greet: function() {
                        console.log("Hello! We are exporting a function called greet!");
                    },
                    add: function(num1, num2) {
                        console.log("The sum is: ", num1, num2);
                    }
                };

        (^ demonstrates basic exporting ^)
        *************************************************************************************************

        2. Importing:
            -i.e. " require("./[+module_path]")
                -DO NOT need ".js" at end of file path
                    -require() method looks for .js files by default
                -DEFAULTS to searching the "node_modules" directory
                    -usually the modules to import are NOT in the same directory as the App
                    -use "./" to prefix the path for any files that are to be found in the current-App's directory
            -will import from other files

        *************************************************************************************************
        i.e.    *APP.JS*

                // imports "my_module" and saves it in a variable that can access it's exports with JSON
                const myCustomModule = require("./my_module");
                myCustomModule.greet()
                myCustomModule.add(5, 7);

                // same thing, but with destructuring
                const { greet, add } = require("./my_module"):
                greet();
                add(5, 7);

        (^ shows how to import another file's exports with and w/out using destructuring ^)
        *************************************************************************************************