Express Route Handlers

In the previous lesson, we wrote the minimum code necessary to run the server and then accessed it through the browser.

Routes

Every application is usually divided into a bunch of routes. Any page or request we invoke on a website is hitting a specific route on the back-end server. Routes determine how each endpoint should be treated and what logic gets executed.

Each HTTP request type is mapped to a routing method in Express with the syntax app.method(path, callback).

Route methods

The path defines the endpoint or the route path, for example, the / root endpoint. After defining the endpoint, we then perform the matched callback function. Here’s a list of the most common route methods:

• The get request handler is used to retrieve resources from the server.
• The put request handleris used for creating and updating the data in the server.
• The post request handler is used to create and update the data in the server. The basic difference between putand post methods is that post is used to create new objects, while put is used to update existing ones.
• The patch request handler is used to update data in the server. The difference between put and patch is that patch is used to update one or two properties of a resource, while put is used to update all properties.
• The delete request handler is used to remove a resource.

Route paths

As we discussed above, the path defines the endpoint that the request is connected to. Paths can be plain strings, string patterns, or regular (regex) expressions. The characters *, +, ?, and () are considered a subset of the regular expressions set, although the - and . characters are interpreted literally as a string in the path.

Handlers

Route handlers

Node.js passes the request to Express, decides which route handler will process the request logic, and then returns a response.

Route handlers are the endpoints responsible for specific services. Here are some ways that route handlers might be used:

• We may use a route handler for authentication purposes. This route may be used to verify if a user exists in the database or not.
• We may use a route handler to register a new user and add them to the database.
• We may have a third route handler to upload a new item. We may need this route to enable the user to upload an image to their account.

Note: Use the npm run start command in the terminal below to run the application.