1. import React from './react';
    2. import ReactDOM from './react-dom';
    3. +let style = { border: '3px solid red', margin: '5px' };
    4. +let element = (
    5. +  <div  id="A1" style={style}>
    6. +    A1
    7. +    <div  id="B1" style={style}>
    8. +      B1
    9. +        <div  id="C1" style={style}>C1</div>
    10. +      <div  id="C2" style={style}>C2</div>
    11. +    </div>
    12. +    <div  id="B2" style={style}>B2</div>
    13. +  </div>
    14. +)
    15. ReactDOM.render(
    16.   element,
    17.   document.getElementById('root')
    18. );