This is brief visualization of the chapter about components:
In React, a component is a building block of the user interface. It can be a function or a class that receives inputs called props and returns a hierarchy of views that represent the UI.
In our application, we have a default component App
let’s run our application, previously just a little bit clean our project:
delete
public
folder,assets
folder,vite
file,index.css
file;remove all unnecessary imports from
App.tsx
file and code fromApp.css
file;and in
App.tsx
file only left this code:import './App.css' function App() { return ( <h1>Hello from default component App.</h1> ) } export default App
Run our application npm run dev
and open it in the browser:
And what we get:
in our index.html file, we have
<div id="root"></div>
- this is our root entry point for UI;in
main.tsx
file we see the code:ReactDOM.createRoot(document.getElementById('root') as HTMLElement).render( <React.StrictMode> <App /> </React.StrictMode>, )
This tells us that we searching for an element with
id=root
and.render
in this element our componentApp
.then let’s check our
App.tsx
file:function App() { return ( <h1>Hello from default component App.</h1> ) } export default App
Here we have a simple functional component
App
that returnsjsx
withh1
element.And now let’s inspect what we have in our HTML:
All is like we expect, we have
div#root
in which we insert ourh1
with text.
Summary
Here we saw an example of a functional React component and how to React works from a code side and for a basic understanding of how it works in UI. More understandable it will be when we will add more pages and will this SPA is in action.
And a couple of words about Class Components. In modern React applications they just don’t use it, even official React documentation told that they switched to functional components. So, don’t see a reason to describe them, maybe only in situations when you will work, for some reason, with a very old React application you can meet Class Components in any other situation better to start using Functional Components.
Previous note - Let’s run our application
Next note - Component Basics