Now, mostly when we will use express. We will use it for 2 things: either to setup APIs or for templates with Server Side Rendering (SSR).

What are differencer between them:

Differences between APIs and SSR:

• In express or in http when we talk about API we means setting up an http interface, to interact with our data. And the data is sent using JSON(JavaScript Object Notation). In order to send back our response we will use res.json() method.
• The res.json() method will do all the heavy lifting, that is for example setting up the proper content type and stringify our data.
• The other flavour we have is SSR, where we will setup templates and send back entire HTML and CSS and JS ourselves, and we will do that using res.render() method.
• We will be starting with APIs.

APIs (Application Programming Interface):

The main idea here is that our server will provide data, and what that means that any frontend app that wants to access it and use it can simply perform a http request, and using our data setup the API and functionality.

APIs can be used in any type of frontend, like react, angular, vanilla js project, etc. It dosen’t matter.

Basic JSON API example:

Here, you can see we have the very basic response from the server.

We can use the data.js provided in the repo for this example: