Pure

Pure.jsx

import React from 'react'

class Pure extends React.PureComponent {
  render() {
    return <div>1</div>
  }
}

class Page extends React.Component {
  render() {
    return (
      <>
        <Pure />                     {/* <= Won't rerender */}
        <Pure>Hello</Pure>           {/* <= Won't rerender */}
        <Pure>{null}</Pure>          {/* <= Won't rerender */}
        <Pure><div /></Pure>         {/* <= Will rerender every time */}
        <Pure>{() => 'Hello'}</Pure> {/* <= Will rerender every time */}
      </>
    )
  }
}