Reading 09

Routing Routing refers to how an application’s endpoints (URIs) respond to client requests. You define routing using methods of the Express app object that correspond to HTTP methods; for example, app.get() to handle GET requests and app.post to handle POST requests.

Basic Route

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

// respond with "hello world" when a GET request is made to the homepage app.get('/', function (req, res) { res.send('hello world') })

Route methods A route method is derived from one of the HTTP methods, and is attached to an instance of the express class.

// GET method route app.get('/', function (req, res) { res.send('GET request to the homepage') })

// POST method route app.post('/', function (req, res) { res.send('POST request to the homepage') })

Route paths Route paths, in combination with a request method, define the endpoints at which requests can be made. Route paths can be strings, string patterns, or regular expressions.

The characters ?, +, *, and () are subsets of their regular expression counterparts. The hyphen (-) and the dot (.) are interpreted literally by string-based paths.

If you need to use the dollar character ($) in a path string, enclose it escaped within ([ and ]). For example, the path string for requests at “/data/$book”, would be “/data/([$])book”.

Route handlers You can provide multiple callback functions that behave like middleware to handle a request. The only exception is that these callbacks might invoke next('route') to bypass the remaining route callbacks. You can use this mechanism to impose pre-conditions on a route, then pass control to subsequent routes if there’s no reason to proceed with the current route.