Routing

September 1, 2017

Routing is all about handling routes, .i.e URL paths. What to do/present/show when someone goes to a route (aka a URL or a path)
routes are URL handling code

code

// Route definition structure
app.METHOD(PATH, HANDLER);

The METHOD could be any http method (GET, POST, PUT, DELETE etc.). You can also use all as a catchall for any method supported in the http module (it'll execute the handler for the URL regardless of the method you are using) app.all(PATH, HANDLER)
The HANDLER could be a callback function, or a file (module) that has the router defined (containing all the routes)

code

// Routing in Express.js
// path: ./routes/index.js
const express = require("express");
const router = express.Router();

router.get("/", (request, response) => {
  response.send("Hey it works!");
});

module.exports = router;

code

// path: ./app.js
const routes = require("./routes/index"); // import our routes

app.use("/", routes); // use the routes file whenever anyone goes to /anything
app.use("/admin", adminRoutes); // You can have multiple route handlers

Callback / Handlers

code

app.all("/secret", (request, response, next) => {
  response.send("ha!");
  next(); // pass control to the next handler
});

In the response (it doesn't have to be called response, it's just a variable name you'll use inside the function, you can call it dodo for all that matters, but you'll most commonly see it defined as res), you can:

console.log() things
send back text .send()
send back JSON data .json()
if you send data twice (e.g. using both .send() and .json()), you're gonna get headers are already sent. So make sure you're never sending data more than once.
next is for when you don't want to send any data back or want to pass it along to something else

code

router.get("/", (req, res) => {
  let profile = { name: "tasiomind", age: 100, cool: true };
  console.log("chal gya!");
  res.send("chal gya code");
  res.json(profile);
});

request.query() access Query strings
request.params() access URL Parameters
request.body() access POSTed values

Query strings

From the request you can extract any data that was passed via the URL

For example:

code

http://localhost:7777/?name=tasiomind&age=100

code

router.get("/", (req, res) => {
  res.send(req.query); // {"name":"\"tasiomind\"","age":"100"}
  res.send(req.query.name); // tasiomind
  res.send(req.query.age); // 100
});

req.query is an object full of all the query parameters

Parameters

: specifies parameters

code

router.get("/profile/:name", (req, res) => {
  // :name is a variable
});

Now it'll handle URLs in the structure of /profile/whomever, where whomever is the value of the name parameter. You can access these parameters values like so:

code

router.get("/profile/:name/:role", (req, res) => {
  // http://127.0.0.1:7777/profile/tasiomind/admin
  res.send(`${req.params.name}'s role is ${req.params.role}`); // tasiomind's role is admin
});

Here's some code to reverse any string sent to a URL endpoint

code

router.get("/reverse/:string", (request, response) => {
  // localhost:port/reverse/tasiomind is awesome
  let reverse = [...request.params.string].reverse().join(""); // using ES6 spread syntax here
  response.send(reverse); // emosewa si hanmaa
});

Routing

Callback / Handlers

Query strings

Parameters

Links