You were right to say express.js is server-side and AngularJS is client-side but, when you said AngularJS can do everything express.js can do, then you are wrong.

The modern AngularJS is now called Angular, so permit me to use it in a modern way.

The routing you see for both express.js and Angular works in seperate ways.

Here is their routing differences:

Express.js (Backend Routing): Decides which data or HTML the server should send based on the request (e.g., /users fetches user data).

Angular (Frontend Routing): Manages which view (page) to show without reloading the browser (e.g clicking a link changes the page instantly, but must fetch the data from whatever backend server it's depending on).

Think of it like this:

Express.js: Server traffic controller (delivers data by processing or fetching database data, and sending it to the frontend via a defined route/api)

Angular: Browser page switcher (changes UI without reloading).

If you don't define a route in express.js, and you point a link from your Angular (frontend), you will be lead to a 404.

Now let's answer your confusion for Node.js, here are their definitions and differences:

Node.js: A backend runtime that runs JavaScript on the server. It handles database interactions, authentication, and business logic.

Express.js: A backend framework based on Node.js that helps manage routes, APIs, and server logic. Think of it as a tool that makes backend development easier (or jquery to JavaScript on the server side. Without Node.js, express.js can't work)

AngularJS/Angular: Frontend frameworks that build interactive user interfaces (UI) running in the browser. They handle how users see and interact with a website.

Let me break something interesting for you, when you see a website built with Angular and assume the backend is runned by express.js, here is how it all makeup the workflow:

° Hosting hardware >

° Install an OS >

° Install and run an environment +

° Install a web server >

° Install express.js >

° Install Angular

• OS (Linux, Windows, Ubuntu (*linux))
• Environment (Node.js, Python, PHP)
• Web server (Apache, nginx, litespeed)
• Express.js can only be installed if Node.js is your running environment.
• Angular (alternatives are Vue.js, React.js e.t.c) in this case, which also have similar routing that you were confused about.

The only visible part users of your website can interact with directly default is the Angular except there's a server misconfiguration or bug.

Note, the running environment and web server have the same system privileges.