6.5 KiB
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¶m2=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.