JAVASCRIPT

before in material ui style

const styles = () =>
  createStyles({
    h: {
      '&::before': {
        content: '"some content"',
        display: 'block',
        height: 60,
        marginTop: -60
      }
    }
  });

before in material ui style

'&::before': {
  content: '""', // "''" will also work.
  ...
}

before in material ui style

'&::before': {
  content: '',
  ...
}

before in material ui style

.makeStyles-content-154:before {
  content: ;
  ...
}