valueTypeExample.js

// @flow

const SIZE = Object.freeze({
 LARGE: "large",
 MEDIUM: "medium",
 SMALL: "small"
})

type ISize = $Values<typeof SIZE>
  
// props type for Avatar component
type IProps = {|
  size: ISize,
|}

const Avatar = (props: IProps) => (
  // ...component details are omitted
)

// this works
<Avatar size={SIZE.LARGE} />
  
// this works as well, althouh it's discouraged
<Avatar size="large" />
  
// this gives an error
<Avatar size="larg" />