IDEXX-Notes/node.md

Node.js

NPM

Whenever creating a new node project, use to set it up

npm init

NPM is a package manager for node.js and js libraries and frameworks. You can look up packages there, and install them for your project with:

npm install package-name --save

module.exports/require

Traditionally, importing JS files into other JS files has not been supported... until now! There are several ways to do this, but node allows you to add things the to module.exports object.

module.exports = 'foo';

Whatever is on there, will be the return value of

require('yourJSFile.js');

You can assign this to a variable to use later

Instantation

First install express with npm install express --save and require it

var express = require('express'); //include express package

express has lots of abilities, but we just want to start up a server app:

var app = express(); // create an express app

Then make it listen on a port

app.listen(3000, function(){ //start the server
	console.log('listening on port ' + PORT);
});

CRUD and HTTP Verbs

In comp sci, there are different kinds of action you can take on data

• create
• read
• update
• destroy

There are different kinds of 'methods' you can use to make a request to a server that map to these actions:

• post (create)
• get (read)
• put/patch (update)
• delete (delete)

PUT is for updating an entire model, PATCH is for changing just a few attributes

Routing

Basic routing can be done at the app level

app.get('/', function(req, res){ // route for /
	res.send('hi'); //respond with 'hi'
});

This sets up an event listener for any GET request that comes into the server with the path of /. Give it a callback function which takes a request variable and a respond variable. Each of these have different methods/properties which we'll learn about

Middleware

We can define a callback function that is called or all requests and then continues on to other request handlers

app.use(function(req, res, next){
	console.log('middleware');
	next();
})

next(); tells express to continue processing the request. app.get(),app.post(), etc have this ability too, but it's rarely used.

Just like with app.get(),app.post(), etc we can add the ability to handle just those requests that match a url pattern

app.use('/foo', function(req, res, next){
	console.log('middleware');
	next();
})

MVC

One of the main goals of express is to cleanly separate data from the view layer. To do this, it follows the Model View Controller pattern, which creates a middleman (Controller) which passes data (Models) off to the presentation/html (View) layer

In addition, putting all your routes inside server.js can become difficult to maintain with a lot of variables. We can group similar urls together into separate "controller" files.

var runsController = require('./controllers/runs.js'); //require our own runsController
app.use('/runs/', runsController); //use it for anything starting with /runs

Now, create a controllers directory, create an appropriately named file, and use:

var controller = require('express').Router(); //require express and create a router (controller)
controller.get('/', function(req, res){ //route for finding all routes by a the session user
	res.send('runs index');
});
module.exports = controller;

Views

Let's separate the views from the controller. Install express with npm install ejs --save

Create a directory called 'views' and create an appropriately named file with the extension .ejs. Now we can reference it. Express will assume the file path starts with the 'views' directory you created.

var controller = require('express').Router(); //require express and create a router (controller)
controller.get('/', function(req, res){ //route for finding all routes by a the session user
	res.render('viewFile.ejs');
});
module.exports = controller;

EJS files are just html, but you can use javascript to dynamically create HTML:

<ul>
	<% for(var i = 0; i < 4; i++) { %>
		<li>
			<%= i %><!-- add = to write a value to the html.  Omit the = and it will just run the JS, but not show anything visually -->
		</li>
	<% } %>
</ul>

You can pass data into the view file by adding a second parameter that's an object. The properties of the object will become the variable name that's accessible in the view file.

var controller = require('express').Router(); //require express and create a router (controller)
controller.get('/', function(req, res){ //route for finding all routes by a the session user
	res.render('viewFile.ejs', {
		variable1Name: 'variable 1 value'
	});
});
module.exports = controller;

Now inside the .ejs file, we can access variable1Name like so:

Value: <%= variable1Name; %>

URL Params/Query Strings

Data can be passed to the server through query strings (a.ka. GET parameters) which look like ?param1=value1&param2=value2

They can be accessed like so:

app.get('/', function(req, res){
	var param1 = req.query.param1;
	var param2 = req.query.param2;
});

Your route can also have parameters in the path section

app.get('/:id', function(req, res){
	var id = req.params.id;
});

Body Parser

We can also pass data to server in the body of the request.

Form data

<form action="/runs" method="POST">
	<input type="text" name="param1"/>
</form>

npm install body-parser --save and require it

var bodyParser = require('body-parser');

Next, tell express to expect form data

app.use(bodyParser.urlencoded({ extended: false })) //tell body parser that we'll be passing in form data

Then, inside any request handler, we can access the form data, formatted as a JS object:

app.post('/run', function(req, res){
	var param1 = req.body.param1;
});

JSON

Install and require body-parser as before, but the middleware changes:

controller.use(bodyParser.json()); //anything handled by this controller is expecting JSON data, not form data

Now instead of using form data, we can use Postman. Create a new tab, choose method, select "body", choose "raw", click on Text dropdown and choose JSON(application/json). Make sure Headers have a line for "Content-Type" set to "application/json"

We can capture the req.body params the same way as with form data.

Method Override

REST

There are seven routes which control basic HTTP operations for data:

https://gist.github.com/alexpchin/09939db6f81d654af06b

URL	HTTP Verb	Action
/photos/	GET	index
/photos/new	GET	new
/photos	POST	create
/photos/:id	GET	show
/photos/:id/edit	GET	edit
/photos/:id	PATCH/PUT	update
/photos/:id	DELETE	destroy

Database

Static

Session

Bcrypt