@react-ui-org/react-ui/src/components/Popover/_helpers/getRootAlignmentClassName.js

React UI is a themeable UI library for React apps.

export default (placement, styles) => {
  const alignment = placement.split('-')[1];

  if (alignment === 'start') {
    return styles.isRootAtStart;
  }

  if (alignment === 'end') {
    return styles.isRootAtEnd;
  }

  return styles.isRootAtCenter;
};