Defining routes in React - Step-by-Step Execution

Concept Flow - Defining routes

Start App

↓

Define Routes

↓

User visits URL

↓

Router matches URL to Route

↓

Render matched Component

↓

Display Component on screen

The app starts by defining routes. When a user visits a URL, the router matches it to a route and renders the correct component.

Execution Sample

React

import { BrowserRouter, Routes, Route } from 'react-router-dom';

function App() {
  return (
    <BrowserRouter>
      <Routes>
        <Route path='/' element={<Home />} />
        <Route path='/about' element={<About />} />
      </Routes>
    </BrowserRouter>
  );
}

export default App;

This code sets up two routes: '/' renders Home component, '/about' renders About component.

Execution Table

Step	User URL	Router Action	Matched Route	Component Rendered
1	/	Check routes	path='/'	Home
2	/about	Check routes	path='/about'	About
3	/contact	Check routes	No match	No component (404 or fallback)
4	Exit	No more URLs	-	-

💡 No more URLs to match, routing ends

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
User URL	''	'/'	'/about'	'/contact'	No more URLs
Matched Route	null	'/'	'/about'	null	null
Component Rendered	null	Home	About	No component (404 or fallback)	No component (404 or fallback)

Key Moments - 2 Insights

Why does the router render no component for '/contact'?

Because '/contact' does not match any defined route path, so no component is rendered as shown in execution_table row 3.

How does the router decide which component to render?

It compares the user URL with each route's path and renders the component of the first matching route, as seen in execution_table rows 1 and 2.

Visual Quiz - 3 Questions

Look at the execution table, what component is rendered when the user visits '/'?

A Home

B About

C Contact

D None

💡 Hint

Check execution_table row 1 under 'Component Rendered'

At which step does the router find no matching route?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at execution_table row 3 under 'Matched Route'

If we add a route for '/contact', how would the component rendered change at step 3?

A It would render Home

B It would render About

C It would render Contact component

D It would still render no component

💡 Hint

Refer to variable_tracker for 'Component Rendered' at step 3 and imagine adding a matching route

Concept Snapshot

Defining routes in React uses <BrowserRouter> to wrap <Routes>.
Inside <Routes>, each <Route> has a path and an element (component).
When user visits a URL, router matches path and renders the element.
No match means no component rendered (can show 404).
Routes must be inside <BrowserRouter> for routing to work.

Full Transcript

This visual execution shows how React routing works by defining routes inside BrowserRouter. When the app starts, routes are set with paths and components. When a user visits a URL, the router checks each route to find a match. If a match is found, it renders the corresponding component. If no match is found, no component is rendered. The execution table traces user URLs and router actions step-by-step. Variable tracker shows how user URL, matched route, and rendered component change over time. Key moments clarify why no component renders for unmatched URLs and how matching works. The quiz tests understanding of route matching and rendering behavior.