Express

Learn Express Routes:

• Express - A powerful and flexible javascript framework for creating web servers and APIs.
• To create a server, you must invoke the express object.

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

• You must specify which port the express object is listening on.

const PORT = 4001;
app.listen(PORT, () => {
  console.log(`Server is listening on port ${PORT}`);
});

• You determine what the Express does by establishing routes.
• Routes define the control flow for requests based on the request’s path and HTTP verb.
• You use app.get() to set up a route and what the route should return.

const moods = [{ mood: 'excited about express!' }, { mood: 'route-tastic!' }];
app.get('/moods', (req, res, next) => {
  // Here we would send back the moods array in response
});

• If no routes are found, it will return a 404 error.
• app.use() will ensure the express is used once the browser is loaded.

app.use(express.static('public'));

• Requests and responses are 1:1. One request returns one response.
• res.send(input) will return any input to the client.
• res.json() will return any json formatted or (javascript object) back to the client.
• When an API request is called, it will search top to bottom for the correct route.
• Routes can be used dynamically. Route parameters start with :
  • /monsters/:id will take any route that includes monsters and a parameter.
  • Parameters are stored in req.params

app.get('/expressions/:id', (req, res, next) => {
  console.log(req.params.id);
  res.send(getElementById(req.params.id, expressions));
});

• Status codes can be attached to responses before being returned to the client.
• Doing res.status() before res.send will change the response code sent back to the client.

res.status(404).send('Monster not found');