I am a new react-js learner and I am having a hard time adding css to my classes that I have inside my react component.
Here is the current code:
import React from 'react';
const Home = () => {
return (
<>
<div class="container">
<h1 class="mainHeader">Home</h1>
<h2>helloo</h2>
</div>
</>
);
};
.container {
// CSS would go here
}
export default Home;
In just HTML and CSS, I was able to apply css on the container div class by just using '.' and whatever the class name was. However, this is giving me an error.
Put the css in its own file, with a .css extension, then import it. Assuming you used create-react-app to set up your project, it will already have appropriate configuration for importing css files. Additionally, you need to use className for the prop, not class
// In a new file home.css:
.container {
// css goes here
}
// In the file you've shown:
import React from 'react';
import './home.css';
const Home = () => {
return (
<>
<div className="container">
<h1 className="mainHeader">Home</h1>
<h2>helloo</h2>
</div>
</>
);
};
export default Home;
Or you can declare it in json format or like you would an object, not in CSS form. Treat it as you are writing in js, which you actually are. See the edit below:
import React from 'react';
const Home = () => {
return (
<>
<div style={container}>
<h1 className="mainHeader">Home</h1>
<h2>helloo</h2>
</div>
</>
);
};
const container = {
// CSS would go here
color: 'red',
background: 'blue'
}
export default Home;
**This is my Styles.css File**
.headingStyle
{font-size:4rem;
color:blue;}
Iam importing these styles here but nothing is being applied to the heading
import React from "react"
import styles from "./Css/styles.css"
function App()
{
return (
<div>
<h1 class={styles.headingStyle}> CSS3 Testimonials Slider</ h1>
</div>
)
}
export default App
According to create-react-app documentation on CSS modules you should name your file styles.module.css and then import it like you already did
import styles from './styles.module.css';
Import CSS file directly.
Use className instead of class
Try this
import React from "react"
import "./Css/styles.css"
function App()
{
return (
<div>
<h1 className="headingStyle"> CSS3 Testimonials Slider</h1>
</div>
)
}
export default App
first of all thank you so much for your time.
My doubt is simple, but i couldn't find a way to get it working.
So... basically i have a '/pages/_app.js' file:
import '../public/styles/global.css';
export default function MyApp({ Component, pageProps }) {
return <Component {...pageProps} />;
}
A global css file '/public/styles/global.css':
:root {
--bg-color: #000;
}
A css module file '/public/styles/header.module.css':
.header {
background-color: var(--bg-color);
}
And finally a home page '/pages/index.js'that uses the css class:
import React from 'react';
import headerStyle from '../public/styles/header.module.css';
export default function Home() {
return <div className={headerStyle.header}>Test</div>;
}
I don't get an error but i didn't manage to refer to the global variables inside the css modules.
Can you guys help me with what am i doing wrong?
If the pages/ directory exists under src/ then the path to the <Home> component should be /src/pages/ and the import for the headerStyle should be the following:
import headerStyle from "../../public/styles/header.module.css";
You just need to go up one more directory.
/*
* #filename /src/pages/index.jsx
*/
import React from "react";
import headerStyle from "../../public/styles/header.module.css";
const Home = () => {
return <div className={headerStyle.header}>Test</div>;
};
export default Home;
Here is a CodeSandbox snippet to demonstrate.
I'm building a React application and I started using CRA. I configured the routes of the app using React Router. Pages components are lazy-loaded.
There are 2 pages: Home and About.
...
const Home = lazy(() => import('./Home'));
const About = lazy(() => import('./About'));
...
<Suspense fallback={<div>Loading...</div>}>
<Switch>
<Route path="/about" component={About} />
<Route path="/" component={Home} />
</Switch>
</Suspense>
...
Each page uses the Button component below.
import React from 'react';
import styles from './Button.module.scss';
const Button = ({ children, className = '' }) => (
<button className={`${styles.btn} ${className}`}>{children}</button>
);
export default Button;
The Button.module.scss file just sets the background color of the button to red.
.btn {
background: red;
}
The Button component accepts a className prop which is then added to the rendered button. This is because I want to give freedom to the consumer of the component. For example, in some pages margins could be needed or the background should be yellow instead of red.
To make it simple, I just want to have a different background color for the Button based on the current page, so that:
Home page => Blue button
About page => Yellow button
Each page is defined as below:
import React from 'react';
import Button from './Button';
import styles from './[PageName].module.scss';
const [PageName] = () => (
<div>
<h1>[PageName]</h1>
<Button className={styles.pageBtn}>[ExpectedColor]</Button>
</div>
);
export default [PageName];
where [PageName] is the name of the page and [ExpectedColor] is the corresponding expected color based on the above bullet list (blue or yellow).
The imported SCSS module, exports a class .pageBtn which sets the background property to the desired color.
Note: I could use a prop on the Button component which defines the variant to display (Blue/Yellow) and based on that prop add a class defined in the SCSS file. I don't want to do that since the change could be something that doesn't belong to a variant (e.g. margin-top).
The problem
If I run the application using yarn start, the application works fine. However, if I build the application (yarn build) and then I start serving the application (e.g. using serve -s build), the behavior is different and the application doesn't work as expected.
When the Home page is loaded, the button is correctly shown with a blue background. Inspecting the loaded CSS chunk, it contains:
.Button_btn__2cUFR {
background: red
}
.Home_pageBtn__nnyWK {
background: blue
}
That's fine. Then I click on the navigation link to open the About page. Even in this case, the button is shown correctly with a yellow background. Inspecting the loaded CSS chunk, it contains:
.Button_btn__2cUFR {
background: red
}
.About_pageBtn__3jjV7 {
background: yellow
}
When I go back to the Home page, the button is now displayed with a red background instead of yellow. That's because the About page has loaded the CSS above which defines again the Button_btn__2cUFR class. Since the class is now after the Home_pageBtn__nnyWK class definition, the button is displayed as red.
Note: the Button component is not exported on the common chunk because its size is too small. Having that in a common chunk could solve the problem. However, my question is about small shared components.
Solutions
I have thought to 2 solutions which, however, I don't like too much:
Increase selectors specificity
The classes specified in the [PageName].module.scss could be defined as:
.pageBtn.pageBtn {
background: [color];
}
This will increase the selector specificity and will override the default Button_btn__2cUFR class. However, each page chunk will include the shared components in case the component is quite small (less than 30kb). Also, the consumer of the component has to know that trick.
Eject and configure webpack
Ejecting the app (or using something like react-app-rewired) would allow specifying the minimum size for common chunk using webpack. However, that's not what I would like for all the components.
To summarize, the question is: what is the correct working way of overriding styles of shared components when using lazy-loaded routes?
You can use the following logic with config file for any pages. Also, You can send config data from remote server (req/res API) and handle with redux.
See Demo: CodeSandBox
create components directory and create files like below:
src
|---components
|---Button
| |---Button.jsx
| |---Button.module.css
Button Component:
// Button.jsx
import React from "react";
import styles from "./Button.module.css";
const Button = props => {
const { children, className, ...otherProps } = props;
return (
<button className={styles[`${className}`]} {...otherProps}>
{children}
</button>
);
};
export default Button;
...
// Button.module.css
.Home_btn {
background: red;
}
.About_btn {
background: blue;
}
create utils directory and create AppUtils.js file:
This file handle config files of pages and return new object
class AppUtils {
static setRoutes(config) {
let routes = [...config.routes];
if (config.settings) {
routes = routes.map(route => {
return {
...route,
settings: { ...config.settings, ...route.settings }
};
});
}
return [...routes];
}
static generateRoutesFromConfigs(configs) {
let allRoutes = [];
configs.forEach(config => {
allRoutes = [...allRoutes, ...this.setRoutes(config)];
});
return allRoutes;
}
}
export default AppUtils;
create app-configs directory and create routesConfig.jsx file:
This file lists and organizes routes.
import React from "react";
import AppUtils from "../utils/AppUtils";
import { pagesConfig } from "../pages/pagesConfig";
const routeConfigs = [...pagesConfig];
const routes = [
...AppUtils.generateRoutesFromConfigs(routeConfigs),
{
component: () => <h1>404 page not found</h1>
}
];
export default routes;
Modify index.js and App.js files to:
// index.js
import React from "react";
import ReactDOM from "react-dom";
import { BrowserRouter as Router } from "react-router-dom";
import App from "./App";
const rootElement = document.getElementById("root");
ReactDOM.render(
<React.StrictMode>
<Router>
<App />
</Router>
</React.StrictMode>,
rootElement
);
...
react-router-config: Static route configuration helpers for React
Router.
// App.js
import React, { Suspense } from "react";
import { Switch, Link } from "react-router-dom";
import { renderRoutes } from "react-router-config";
import routes from "./app-configs/routesConfig";
import "./styles.css";
export default function App() {
return (
<div className="App">
<ul>
<li>
<Link to="/">Home</Link>
</li>
<li>
<Link to="/about">About</Link>
</li>
</ul>
<Suspense fallback={<h1>loading....</h1>}>
<Switch>{renderRoutes(routes)}</Switch>
</Suspense>
</div>
);
}
create pages directory and create files and subdirectory like below:
src
|---pages
|---about
| |---AboutPage.jsx
| |---AboutPageConfig.jsx
|
|---home
|---HomePage.jsx
|---HomePageConfig.jsx
|
|---pagesConfig.js
About Page files:
// AboutPage.jsx
import React from "react";
import Button from "../../components/Button/Button";
const AboutPage = props => {
const btnClass = props.route.settings.layout.config.buttonClass;
return (
<>
<h1>about page</h1>
<Button className={btnClass}>about button</Button>
</>
);
};
export default AboutPage;
...
// AboutPageConfig.jsx
import React from "react";
export const AboutPageConfig = {
settings: {
layout: {
config: {
buttonClass: "About_btn"
}
}
},
routes: [
{
path: "/about",
exact: true,
component: React.lazy(() => import("./AboutPage"))
}
]
};
Home Page files:
// HomePage.jsx
import React from "react";
import Button from "../../components/Button/Button";
const HomePage = props => {
const btnClass = props.route.settings.layout.config.buttonClass;
return (
<>
<h1>home page</h1>
<Button className={btnClass}>home button</Button>
</>
);
};
export default HomePage;
...
// HomePageConfig.jsx
import React from "react";
export const HomePageConfig = {
settings: {
layout: {
config: {
buttonClass: "Home_btn"
}
}
},
routes: [
{
path: "/",
exact: true,
component: React.lazy(() => import("./HomePage"))
}
]
};
...
// pagesConfig.js
import { HomePageConfig } from "./home/HomePageConfig";
import { AboutPageConfig } from "./about/AboutPageConfig";
export const pagesConfig = [HomePageConfig, AboutPageConfig];
Edited section:
With HOC Maybe this way: CodeSandBox
create hoc dir and withPage.jsx file:
src
|---hoc
|---withPage.jsx
...
// withPage.jsx
import React, { useEffect, useState } from "react";
export function withPage(Component, path) {
function loadComponentFromPath(path, setStyles) {
import(path).then(component => setStyles(component.default));
}
return function(props) {
const [styles, setStyles] = useState();
useEffect(() => {
loadComponentFromPath(`../pages/${path}`, setStyles);
}, []);
return <Component {...props} styles={styles} />;
};
}
And then pages like below:
src
|---pages
|---about
| |---About.jsx
| |---About.module.css
|
|---home
|---Home.jsx
|---Home.module.css
About.jsx file:
// About.jsx
import React from "react";
import { withPage } from "../../hoc/withPage";
const About = props => {
const {styles} = props;
return (
<button className={styles && styles.AboutBtn}>About</button>
);
};
export default withPage(About, "about/About.module.css");
About.module.css file:
// About.module.css
.AboutBtn {
background: yellow;
}
Home.jsx file:
// Home.jsx
import React from "react";
import { withPage } from "../../hoc/withPage";
const Home = props => {
const { styles } = props;
return <button className={styles && styles.HomeBtn}>Home</button>;
};
export default withPage(Home, "home/Home.module.css");
Home.module.css file:
// Home.module.css
.HomeBtn {
background: red;
}
I would suggest instead of adding both the default styles and the consumer styles, use the consumer's styles over yours and use your as a callback if not supplied. The consumer can still compose your defaults with the composes keyword.
Button.js
import React from 'react';
import styles from './Button.module.scss';
const Button = ({ children, className}) => (
<button className={className ?? styles.btn}>{children}</button>
);
export default Button;
SomePage.module.scss
.pageBtn {
// First some defaults
composes: btn from './Button.module.scss';
// And override some of the defautls here
background: yellow;
}
If you wish, use sass #extends or #mixin instead
EDIT: Haven't tested it, but could it be that just by using composes webpack will make sure to bundle the defaults only once? Thus you're no longer needed to change your Button.js code with the ??
Solution 1
I know this is very obvious, but would work anyway:
Set !important on your overwriting css rules, thus bypassing specificity:
[PageName].module.scss:
.btn {
color: yellow !important;
}
However, most of the strict devs I know would avoid this keyword at all cost.
Why ?
Because when you start to have a lot of !important your css is a nightmare to debug. If you start writing !important rules with higher specificity, you know you have gone too far
It is only meant for corner-cases like yours, you might as well use it.
Solution 2
fix CRA config to enforce style tags order.
It is open-source after all :)
You can give your input on this bug here (upvote might give it more visibility):
https://github.com/facebook/create-react-app/issues/7190
Solution 3 (Update)
You could create a SCSS mixin in a new customButton.scss file, to generate css rules with higher specificity:
// customButton.scss
#mixin customBtn() {
:global {
.customBtn.override {
#content;
}
}
}
We will use two static class names (using the :global selector), because that way their name won't change based on where they are imported from.
Now use that mixin in your pages' SCSS:
// [pageName].module.scss
#import 'customButton.scss';
#include customBtn {
color: yellow;
}
css output should be:
.customBtn.override {
// put everything you want to customize here
color: yellow;
}
In Button.jsx: apply both class names to your button in addition to styles.btn:
// Button.jsx
const Button = ({ children, className = '' }) => (
<button className={`${styles.btn} customBtn override ${className}`}>
{children}
</button>
);
(Note that these are not referenced through the styles object, but the classname directly)
The main drawback is these are not dynamic class names, so you have to watch out to avoid conflicts yourself like we use to do before.
But I think it should do the trick
I create a simple react/electron project with "electron-forge" plugin : electron-forge init myProject --template=react. I try to import my css file with this code below
Button.module.css
.error {
color: red;
}
app.jsx - created by electron-forge:
import React from 'react';
import styles from './Button.module.css'; // Import css modules stylesheet as styles
export default class App extends React.Component {
render() {
return (
<div>
<h1>Hello world</h1>
<button className={styles.error}>Error Button</button>
</div>
)
}
}
It throws an error:
Uncaught Error: Couldn't find a compiler for /home/denny/Experimentals/electron-transactionsell/src/Button.module.css
I'm pretty sure I have the file in the correct folder
and I am sure that this is how it's done in React
https://facebook.github.io/create-react-app/docs/adding-a-css-modules-stylesheet