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50 lines
1.6 KiB
Markdown
50 lines
1.6 KiB
Markdown
---
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id: faq-styling
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title: Styling and CSS
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permalink: docs/faq-styling.html
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layout: docs
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category: FAQ
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---
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### How do I add CSS classes to components?
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Pass a string as the `className` prop:
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```jsx
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render() {
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return <span className="menu navigation-menu">Menu</span>
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}
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```
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It is common for CSS classes to depend on the component props or state:
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```jsx
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render() {
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let className = 'menu';
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if (this.props.isActive) {
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className += ' menu-active';
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}
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return <span className={className}>Menu</span>
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}
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```
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If you often find yourself writing code like this, [classnames](https://www.npmjs.com/package/classnames) package can simplify it.
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### Can I use inline styles?
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Yes, see the docs on styling [here](/docs/dom-elements.html#style).
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### Are inline styles bad?
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CSS classes are generally more efficient than inline styles.
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### What is CSS-in-JS?
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"CSS-in-JS" refers to a pattern where CSS is composed using JavaScript instead of defined in external files. Read a comparison of CSS-in-JS libraries [here](https://github.com/MicheleBertoli/css-in-js).
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_Note that this functionality is not a part of React, but provided by third-party libraries._ React does not have an opinion about how styles are defined; if in doubt, a good starting point is to define your styles in a separate `*.css` file as usual and refer to them using [`className`](/docs/dom-elements.html#classname).
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### Can I do animations in React?
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React can be used to power animations. See [React Transition Group](https://reactcommunity.org/react-transition-group/) and [React Motion](https://github.com/chenglou/react-motion), for example.
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