React Component SCSS available for all Components

Question

I just started learning ReactJS and I made a Project with .scss

For some reason when I add a style in a .scss file that style also changes other components' styles as well.

example: I add a li style in the Home.scss, but it will change the style of the Footer component's li too. I didn't import it into the Footer.js or anything.

Does anyone know what is the reason why does it do it, and what is the solution?

Answer 1

Adding a className per component won't solve your problem, it will work as expected until you have any nested component.

Because if you add

#component-name {
  li {
    ...
  }
}

The CSS will be applied to any component inside of that component too.

To limit your CSS to a component in react, you have a few options :

CSS Modules

Create React App supports CSS Modules out of the box (as of version 2)
It works with SCSS too (YourComponent.module.scss)

YourComponent.js:

import styles from './YourComponent.module.css'

export const YourComponent () => {
  <ul>
    <li className={styles.yourLi}>
  </ul>
}

YourComponent.module.scss:

.yourLi {
  color: blue;
}

CSS-in-JS

With this method, as the name suggests, you can declare your CSS within your JS. There are multiple libraries to implement this.

Styled-Components

Here is an example with styled components which is the one that seems to be the most used as of today:

const YourLi = styled.li`
  display: inline-block;
  border-radius: 3px;
  padding: 0.5rem 0;
  margin: 0.5rem 1rem;
  width: 11rem;
  background: transparent;
  color: white;
  border: 2px solid white;
`  

render(
  <div>
    <ul>
      <YourLi>
        Your styled li
      </YourLi>
    </ul>
  </div>
)