CSS pseudo elements in React

Depending if you only need a couple attributes to be styled inline you can do something like this solution (and saves you from having to install a special package or create an extra element):

https://stackoverflow.com/a/42000085

<span class="something" datacustomattribute="👋">
  Hello
</span>

.something::before {
  content: attr(datascustomattribute);
  position: absolute;
}

Note that the datacustomattribute must start with data and be all lowercase to satisfy React.

Inline styles cannot be used to target pseudo-classes or pseudo-elements. You need to use a stylesheet.

If you want to generate CSS dynamically, then the easiest way is to create a DOM element <style>.

<style dangerouslySetInnerHTML={{
  __html: [
     '.my-special-div:after {',
     '  content: "Hello";',
     '  position: absolute',
     '}'
    ].join('\n')
  }}>
</style>
<div className='my-special-div'></div>

Got a reply from @Vjeux over at the React team:

Normal HTML/CSS:

<div class="something"><span>Something</span></div>
<style>
    .something::after {
    content: '';
    position: absolute;
    -webkit-filter: blur(10px) saturate(2);
}
</style>

React with inline style:

render: function() {
    return (
        <div>
          <span>Something</span>
          <div style={{position: 'absolute', WebkitFilter: 'blur(10px) saturate(2)'}} />
        </div>
    );
},

The trick is that instead of using ::after in CSS in order to create a new element, you should instead create a new element via React. If you don't want to have to add this element everywhere, then make a component that does it for you.

For special attributes like -webkit-filter, the way to encode them is by removing dashes - and capitalizing the next letter. So it turns into WebkitFilter. Note that doing {'-webkit-filter': ...} should also work.