fishcharlie/more-express-routes

[js, node, express, routes]

More Express:

Objectives
Explain parsing URL params and using query string params
Apply routing knowledge to build an Express application with dynamic routes
Explain the usefulness of middleware (e.g., body-parser)

Pre-reading

• HTTP Intro

Terminology

• HTTP
• Resource path
• Query string
• HTTP verb
• Status code
• Middleware

Outline

• Intro
• Routing
  • HTTP GET
• Exercises

Setup

Let's start with a simple Express application.

• Inside your fork of this repo, make a directory and index.js

  mkdir quick_example
  cd quick_example/
  touch index.js

• Then create a package.json, use the first line below or npm init.

  echo {} > package.json      #puts an empty object into a new `package.json`
  npm install --save express
  subl .

The folder structure will be as follows:

/quick_example
    /node_modules
        /express
            ...
    index.js
    package.json

Now we need write some code for our simple application.

index.js

// requirements
var express = require('express'),
    app = express();

// a "GET" request to "/" will run the function below
app.get("/", function (req, res) {
    // send back the response: 'Hello World'
    res.send("Hello World");
});

// start the server
app.listen(3000, function () {
    console.log("Go to localhost:3000/");
});

Now you can start the server:

node index.js

What is Routing (RESTful review)?

Building an application will require us to have a firm grasp of something we call routing. Each route is a combination of a Request Type and Path.

Request Type	Request Path	Response
GET	/	Hello World
GET	/burgers	Hamburger, Cheese Burger, Dble Cheese Burger
GET	/tacos	Soft Taco, Crunchy Taco, Super Taco

Let's build these into our application:

index.js

var express = require('express')
var app = express();

var burgers = [
                "Hamburger",
                "Cheese Burger",
                "Dble Cheese Burger"
               ];

var tacos = [
                "Soft Taco",
                "Crunchy Taco",
                "Super Taco"
               ];

app.get("/", function (req, res) {
    res.send("Hello World");
});

app.get("/burgers", function (req, res) {
    //send all the burgers     
    res.send(burgers.join(", "));
});

app.get("/tacos", function (req, res) {
    //send all the tacos           
    res.send(tacos.join(", "));
});

app.listen(3000, function () {
    console.log("Go to localhost:3000/");
});

Request (Url) Parameters

What if we want to create an app that can dynamically say hello to anyone?

• Using url parameters add a dynamic route to the application, indicated by : and the variable name you want to use, we'll use :name for the example below.

app.get("/greet/:name", function (req, res) {
    res.send( "Hello, " + req.params.name );
});

Here we are seeing the first introduction to parameters that the application can identify. In the following route :name is consider a route parameter. We can access it using req.params.name.

Request Type	Request Path	Response
GET	/greet/:name	Hello, :name

Query Params

Generally, you don't want to cram everything into a route. Just imagine when there are multiple parameters in route. Or maybe we don't care about getting the order of the parameters correct. Luckily, there are query parameters you can include with each request.

Let's see query params in action. Go to https://google.com/search?q=kittens&tbm=isch

• ? denotes the beginning of the query parameters
• = indicates an assignment; anything to the left is the key, while the right represents the value
• & allows for the input of multiple parameters, separating each

Let's add our first route to practice query params.

app.get("/thank", function (req, res) {
    var name = req.query.name;
    res.send("Thank you, " + name);
});

Reset your server and go to localhost:3000/thank?name=jane. Note how we can now define parameters in the url after a ?.

Middleware (Review)

What is middleware? In terms of Express, middleware is a function with access to the request object (req), the response object (res), and the next middleware in the application’s request-response cycle, commonly denoted by a variable named next.

Middleware can:

• Execute any code.
• Make changes to the request and the response objects.
• End the request-response cycle.
• Call the next middleware in the stack.

You can create your own middleware, or use third-party modules. That's right, there are tons of useful middlewares that are already out there which you can use to handle common challenges like authentication, validations, and parsing.

The body-parser module is an example of some middleware that makes Express awesome. You can use it to parse out params from the POST'd form. This provides a different way to collect data instead of relying on URL or query params.

Summary

We learned about

• Routing to different resources, i.e. /burgers and /tacos
• Using dynamic parameters, i.e. /burgers/:index and /tacos/:index to request specific data
• Using query parameters for dynamic requests to serve up dynamic responses
• What middleware is and why it is helpful

This will be essential knowledge for building and interacting with applications that contain multiple resources, such as users, posts, comments, etc.

Exercises

Now let's jump into a routing challenge. Follow this link and complete them in your fork of this repo, then push all your changes up to your remote repo.