Develop Reference

Maintain context values between routes in React.js

I'm trying to maintain state values between routes in context. But it gets reset when the route changes.
aackage.json:
"react-router-dom": "^6.8.0",
"react-dom": "^18.2.0",
"react": "^18.2.0",
App.js:
export default const App = () => {
const [loading, setLoading] = useState(false);
const [data, setData] = useState(null);
const getData = async () => {
setLoading(true);
const data = await axios.get("url", {
withCredentials: true,
});
setData(data);
setLoading(false);
};
useEffect(() => {
getData()
console.log("I run on route change");
}, []);
const GlobalContextValue= {
data: data,
loading: loading,
};
return (
<>
<GlobalContextProvider value={GlobalContextValue}>
<BrowserRouter>
<Routes>
<Route index element={<HomePage />} />
<Route path="/:slug" element={<PostPage />} />
{/* <Route path="*" element={<NoPage />} /> */}
</Routes>
</BrowserRouter>
</<GlobalContextProvider />
</>
)
}
Whenever I try to access any route the getData function inside the useEffect calls which inturns resets the data. I have attached a CodeSandbox to replicate the same
I don't know if this problem is related to reactJs or react-router. Thanks in advance

As you don't seem to have any navigation link, I assume you are using the browser search bar, or a normal HTML <a> tag. Well, doing so refreshes the page, so the entire app gets re-created.
Using useNavigate or Link from React Router Dom, doesn't refresh the page, hence your context data remains untouched:
const HomePage = () => {
return (
<>
<h1>Hii Homepage </h1>
<Link to="/1">Go to PostPage</Link>
</>
);
};
const PostPage = () => {
const params = useParams();
return (
<>
<h1>Hii PostPage {params.slug} </h1>
<Link to="/">Go to HomePage</Link>
</>
);
};
export default function App() {
useEffect(() => {
console.log(
"I run on load and route change with browser search bar, not with useNavigate or Link"
);
}, []);
return (
<>
{/* This context wrapping BrowserRouter keeps its value if you navigate with Link or
useNavigate. */}
<GlobalContextProvider value={{ key: "some value" }}>
<BrowserRouter>
<Routes>
<Route index element={<HomePage />} />
<Route path="/:slug" element={<PostPage />} />
{/* <Route path="*" element={<NoPage />} /> */}
</Routes>
</BrowserRouter>
</GlobalContextProvider>
</>
);
}

React shows another page and then the Homepage, whe navigating to Homepage

I am new to React and I am using the Traversy crash course and the extra video about the react router 6+.
My Routes are like
import { BrowserRouter as Router, Route, Routes } from 'react-router-dom'
return (
<div className="container">
<Router>
<Header
title='sikyona'
onAdd={()=> setShowAddtask(!showAddTask)}
showAdd={showAddTask}
/>
<Routes>
<Route
path='/'
element={
<>
{showAddTask && <AddTask onAdd={addTask} />}
{tasks.length > 0
? <Tasks tasks={tasks} onDelete={deleteTask} />
:<p>add tasks</p>
}
</>
}
/>
<Route path='/about' element={<About/>} />
</Routes>
<Footer />
</Router>
</div>
);
The problem is that when I navigate to the homepage http://localhost:3000/ I first see the About page for a second, and then the homepage (Route path='/'...)
I have "react-router-dom": "^6.4.1",
What is this happening and how can I fix it?

The issue isn't that the "About" page or About component is being rendered when the app is loading or navigating to "/" for the first time. It's that the app is actually on "/" and there's no tasks to display just yet and the UI is rendering the container, Header, the Route for path="/" with the "add tasks" text, and the Footer which renders a link to "/about".
Contrast this rendered UI with the actual "/about" path and About component.
Perhaps the UI/UX is fine for you with regards to this behavior and understanding what exactly is being rendered when, and for what reason. If on the other hand you don't want to see any of the UI until data has been loaded you can tweak the code to render nothing or some loading indicator while the tasks are fetched.
Example:
function App() {
const [showAddTask, setShowAddtask] = useState(false);
const [tasks, setTasks] = useState(); // <-- initially undefined
useEffect(() => {
const getTasks = async () => {
try {
const tasks = await fetchTasks();
setTasks(tasks); // <-- defined and populated
} catch(error) {
// log errors, display message, etc... or ignore
setTasks([]); // <-- defined and empty
}
};
getTasks();
}, []);
...
if (!tasks) {
return null; // <-- return null or loading indicator/spinner/etc
}
return (
<div className="container">
<Router>
<Header
title="hello"
onAdd={() => setShowAddtask(show => !show)}
showAdd={showAddTask}
/>
<Routes>
<Route
path="/"
element={
<>
{showAddTask && <AddTask onAdd={addTask} />}
{tasks.length ? (
<Tasks tasks={tasks} onDelete={deleteTask} />
) : (
<p>add tasks</p>
)}
</>
}
/>
<Route path="/about" element={<About />} />
<Route path="/task-details/:id" element={<TaskDetails />} />
</Routes>
<Footer />
</Router>
</div>
);
}

Try to put your <Route path='/' /> last in the list.

How to detect matched route from a component outside of the <Route/> component that was matched using react-router?

I've got the following structure in my React app, using react-router-dom.
<Router>
<Header/>
<Main>
<AllRoutes> // THIS HANDLES THE SWITCH WITH ALL THE ROUTES
<Switch>
<Route exact path={ROUTES.HOME} component={Home}/>
<Route exact path={ROUTES.ABOUT} component={About}/>
<Route exact path={ROUTES.PRIVACY} component={Privacy}/>
// ETC
</Switch>
</AllRoutes>
</Main>
<Footer/> // <==== FOOTER NEEDS TO KNOW WHICH ROUTE HAS BEEN MATCH
<Router>
QUESTION
Footer needs to know what <Route/> has been match. What is the best pattern to achieve that?
OPTION #1
I found the useRouteMatch hook over on react router docs:
This would kind of work, but I don't think it is good enough for my situation. Because a URL string can match a route and still don't be a valid route at the same time.
For example:
Route: /:language/privacy
Valid route: /en/privacy
Not valid route that would also match: /notALanguage/privacy
Once a route has match, I usually need to check if it is valid before rendering a component page or the 404 page.
Like:
<Route exact path={"/:language/privacy"} render={(routeProps) => {
const possibleLanguage = routeProps.match.params.language;
if (possibleLanguage in LANGUAGES) {
return(
<PrivacyPage lang={possibleLanguage}/>
);
}
else {
return(
<Page404/>
);
}
}}/>
OPTION #2
What I'm thinking about doing is:
App.js calls useLocation. So it always re-render when there is a route change.
I could add a detectRoute function in App.js to do all the route checking beforehand.
And my AllRoutes component wouldn't need a component. I would implement a native JS switch and render the corresponding route.
This way I know upfront which <Route/> is going to match and I can pass it on to <Footer/> or any component that lives outside of the matched <Route/>.
Something like this:
SandBox Link
export default function App() {
console.log("Rendering App...");
const location = useLocation();
// THIS WOULD BE THE detectRoute FUNCTION
// I COULD EVEN USE THE useRouteMatch HOOK IN HERE
const matchedRoute =
location.pathname === ROUTE1
? "ROUTE1"
: location.pathname === ROUTE2
? "ROUTE2"
: "404";
return (
<div>
<div className="App">
<Link to={ROUTE1}>Route 1</Link>
<Link to={ROUTE2}>Route 2</Link>
<Link to={"/whatever"}>Route 404</Link>
</div>
<div>
<AllRoutes matchedRoute={matchedRoute} />
</div>
</div>
);
}
function AllRoutes(props) {
switch (props.matchedRoute) {
case "ROUTE1":
return <Route exact path={ROUTE1} component={Page1} />;
case "ROUTE2":
return <Route exact path={ROUTE2} component={Page2} />;
default:
return <Route exact path={"*"} component={Page404} />;
}
}
It works. But I would like to know if there's a proper way of doing this, 'cause this seems a bit weird and there might be something out there that was specifically designed for this.

Generally you want to either:
Wrap the components together
Create another switch to route them (and pass match params)
I put together a somewhat comprehensive example of the options. Hope that helps!
import React from "react";
import "./styles.css";
import { Switch, Link, Route, BrowserRouter } from "react-router-dom";
const hoc = (Component, value) => () => (
<>
<main>
<Component />
</main>
<Footer value={value} />
</>
);
const Wrapper = ({ component: Component, value }) => (
<>
<main>
<Component />
</main>
<Footer value={value} />
</>
);
const WrapperRoute = ({ component, value, ...other }) => (
<Route
{...other}
render={props => <Wrapper component={component} value={value} {...props} />}
/>
);
const Footer = ({ value }) => <footer>Footer! {value}</footer>;
const Header = () => <header>Header!</header>;
const Another = () => <Link to="/onemore">One More!</Link>;
const Home = () => <Link to="/other">Other!</Link>;
const OneMore = () => <Link to="/">Home!</Link>;
const Other = () => <Link to="/another">Another!</Link>;
export default () => (
<BrowserRouter>
<Header />
<Switch>
{/* You could inline it! */}
<Route
path="/another"
render={() => (
<>
<main>
<Another />
</main>
<Footer value="" />
</>
)}
/>
{/* You could use a custom route component (that uses an HOC or a wrapper) */}
<WrapperRoute
component={OneMore}
path="/onemore"
value="I got one more!"
/>
{/* You could use a Higher-Order Component! */}
<Route path="/other" component={hoc(Other, "I got other!")} />
{/* You could use a wrapper component! */}
<Route
path="/"
render={() => <Wrapper component={Home} value="I got home!" />}
/>
</Switch>
{/* You could have another switch for your footer (inline or within the component) */}
<Switch>
<Route
path="/another"
render={() => <Footer value="Switch footer another!" />}
/>
<Route
path="/other"
render={() => <Footer value="Switch footer other!" />}
/>
<Route
path="/onemore"
render={() => <Footer value="Switch footer onemore!" />}
/>
<Route path="/" render={() => <Footer value="Switch footer home!" />} />
</Switch>
</BrowserRouter>
);
Note the WrapperRoute would allow you to do validation on your match params before passing them through. You could do a Redirect if needed.

What I've ended up doing:
Since I'm using Redux, I added a piece of global state to keep track of the matched route.
And I dispatch actions to update that state from the render prop from the <Route/>'s component.
<Switch>
<Route key={index} exact path={"/some-route"} render={(routeProps) => {
// HERE I DISPATCH AN ACTION TO CHANGE THE STATE FOR THE CURRENT ROUTE
dispatch({
type: UPDATE_CURRENT_ROUTE,
payload: { name: "SOME_ROUTE_NAME" }
});
return (
<PrivacyPage
{...routeProps}
/>
);
}}/>
</Switch>
And now I can do on Footer.js:
function Footer() {
const currentRoute = useSelector((state) => state.currentRoute);
// RENDER FOOTER ACCORDINGLY TO THE CURRENT ROUTE
}

React Router active Class for home page

I've got a navigation that I am having a hard time trying to style. I have been able to add active classes to the navigational elements and apply styles to them, however the main dashboard which functions as a homepage does not get the dedicated active class applied to it when I click it. After doing a little bit of digging around in the app, I believe the AppRouter.js or routeConfig.js might be the issue.
The navigational elements are displayed with the Navlink code below:
renderNavigationItem = (navigationItem) => {
const { classes } = this.props;
const { id, name, parentUrlLink } = navigationItem;
return (
<NavLink exact key={id.toString()} to={{ pathname: parentUrlLink }} className="desk-link"
activeClassName='is-active'>
<MenuItem className={classes.fontBoldHeader}>{name}</MenuItem>
</NavLink>
);
}
The app router looks like this:
class AppRouter extends Component {
constructor(props, context) {
super(props);
this.context = context;
}
render() {
const { account } = this.context;
return (
<Switch>
{account ? <Redirect exact from="/" to={{ pathname: '/dashboard' }} /> : <Route exact path="/" component={Home} />}
{routes.map((item) => <PrivateRoute {...item} key={`${item.path}-route`} />)}
<Route path="/sessiontimeout" render={(props) => <TimedOutPage {...props} />} />
<Route path="/500" render={(props) => <Error errorCode="500" {...props} />} />
<Route path="/503" render={(props) => <Error errorCode="503" {...props} />} />
<Route path="*" render={(props) => <Error errorCode="404" {...props} />} />
</Switch>
);
}
}
It looks like there's a specific rule that is in place for the "dashboard" page. It is also the page people go to if they click the logo so I feel like there is a specific rule that is preventing the dashboard page to inherit the "is-active" class. I am new to React so this is something that is a little over my head at the moment and any help would be greatly appreciated!
Edit: Here is where rednerNavigation is called:
renderNavigation = () => {
const { menuNavigation } = this.props;
return menuNavigation.map((item) => {
if (item.children.length > 0) {
return this.renderNavigationItemWithSubNav(item);
}
return this.renderNavigationItem(item);
});
}

How to change NavBar text on login/logout in React.JS?

I have a Navigation bar in my project which I call from inside App.js. Based on if I am logged in or not, I want to render different views of NavBar. If logged in, I want the NavBar to have a logout button. And if logged out, I want the NavBar to have login button. I use a token in localStorage to check if I am logged in or not. When logged in, token is present in localStorage. On logout/before login, there is no token key in localStorage. I pass this token as a state to NavBar as shown:
export default function App() {
const [loggedIn, setLoggedIn] = useState(localStorage.getItem("token"));
return (
<div>
<Router>
<Navbar isAuth={loggedIn} />
<Route exact path="/" exact component={Home} />
<Route path="/login" component={Login} />
<PrivateRoute path="/dashboard" component={Dashboard} />
</Router>
</div>
);
}
Now from NavBar component, I use this prop to render different views of NavBar as shown below:
const NavBar = props => {
const classes = useStyles();
if (props.isAuth !== null) {
return (
<div className={classes.root}>
<AppBar position="static">
<Toolbar>
<Typography variant="h6" className={classes.title}>
<Link
href="/"
style={{ textDecoration: "none", color: "white" }}
>
Timetracker
</Link>
</Typography>
<Link href="/" style={{ color: "white" }}>
<Button color="inherit" onClick={auth.logout}>
Logout
</Button>
</Link>
</Toolbar>
</AppBar>
</div>
);
} else {
return (
<div className={classes.root}>
<AppBar position="static">
<Toolbar>
<Typography variant="h6" className={classes.title}>
<Link
href="/"
style={{ textDecoration: "none", color: "white" }}
>
Timetracker
</Link>
</Typography>
<Link href="/login" style={{ color: "white" }}>
<Button color="inherit">Login</Button>
</Link>
</Toolbar>
</AppBar>
</div>
);
}
};
export default NavBar;
The problem is that, the NavBar does not update itself as soon as I login. I have to manually refresh the page in order to render the new NavBar. Similarly on logout too, It does not update itself and updates only on manual refresh. What is the issue and how to solve this?

I found a simple solution:
use a componentDidMount() or useEffect() function which will render automatically upon loading the NavBar page.
Inside this function, use a setInterval() function to continually retrieve the auth status (say, an interval of 5000). This will continually refresh the NavBar, and change the button immediately.
I imagine you would have to put the auth check in the NavBar component itself, instead of using props. I put the specific buttons I wanted to change in a separate component called NavBarUser, which changes 'login | signup' to 'logout' and contains a user avatar. I then inserted this component into the NavBar itself at the appropriate place.
This is what my code looks like:
```
import React, { useState, useEffect } from 'react';
import Avatar from './Avatar';
import { BrowserRouter as Router, Link } from 'react-router-dom';
const NavBarUser = () => {
const [user, setUser] = useState({});
useEffect(() => {
{ /*
setInterval was used in order to refresh the page constantly
in order to have the "logout" button show immediately in place of
"login", as soon as user logs out.
*/}
setInterval(() => {
const userString = localStorage.getItem("user");
const user = JSON.parse(userString);
setUser(user);
}, [])
}, 5000);
const logout = () => {
return localStorage.removeItem("user");
}
if (!user) {
return (
<div className="navbar-nav ml-auto">
<Link to="/login" className="nav-item nav-link">Login</Link> <span
className="nav-item nav-link">|</span> <Link to="/SignUp" className="nav-item nav-
link">Sign Up</Link>
</div>
)
}
if (user) {
return (
<div className="navbar-nav ml-auto">
<Link to="/" className="nav-item nav-link" onClick={logout}>Logout</Link>
<Avatar img="/images/Eat-healthy.jpg" />
</div>
)
}
}
export default NavBarUser;
```

You need to add <Switch> as well. From the documentation:
Renders the first child or that matches the location.
<Switch> is unique in that it renders a route exclusively. In contrast, every <Route> that matches the location renders inclusively.
Just like the following:
<Router>
<Switch>
<Navbar isAuth={loggedIn} />
<Route exact path="/" exact component={Home} />
<Route path="/login" component={Login} />
<PrivateRoute path="/dashboard" component={Dashboard} />
</Switch>
</Router>
Read further here: Router
I hope that helps!

Your app's state won't update if you change the value of the token in localStorage.
You need to make sure you update the state, I've added a sandbox if it helps.

Here's how I solved this issue:
To start, I created a isLoggedIn state in my App class. I gave it a componentDidMount() method that would fetch the login state from a cookie on app start. Then I created globalLogin and globalLogout methods as arrow functions, which set the isLoggedIn state to true or false accordingly. I passed my Nav component the isLoggedIn state as a prop and passed the Login and Nav routes the globalLogin and globalLogout methods. These methods can then be called from Login or Nav with this.props.globalLogout(); or this.props.globalLogin();.
This is a simplified version of my App.js.
class App extends Component {
constructor(props){
super(props);
this.state = {
isLoggedIn: false,
}
}
componentDidMount() {
const token = Cookie.get("token") ? Cookie.get("token") : null;
if (token) {
this.setState({ "isLoggedIn": true });
}
}
globalLogin = () => {
this.setState({ "isLoggedIn": true });
}
globalLogout = () => {
this.setState({ "isLoggedIn": false });
}
render() {
return (
<Router>
<div className="App">
<Nav isLoggedIn={this.state.isLoggedIn} globalLogout={this.globalLogout}/>
<Switch>
<Route path="/" exact component={Home} />
<Route path="/login" exact>
<Login globalLogin={this.globalLogin}/>
</Route>
</Switch>
</div>
</Router>
);
}
}
EDIT: using history.push didn't work in login module above so I added an intermediate to handle props
render() {
const LoginIntermediate = (props) => {
return (
<Login {...props} globalLogin={this.globalLogin}/>
)
}
return (
<Router>
<div className="App">
<Nav isLoggedIn={this.state.isLoggedIn} globalLogout={this.globalLogout}/>
<Switch>
<Route path="/" exact component={Home} />
<Route path="/login" exact component={LoginIntermediate} />
</Switch>
</div>
</Router>
);
}