score:0

you forgot to declare the datatype. also export default app are not required.

score:0

  1. you are trying to use hi before declaring it
  2. you are exporting app without declaring it anywhere

let's try

import react, { component } from 'react';

import reactdom from 'react-dom';

let hi = <h1>hello</h1>
reactdom.render(hi,document.getelementbyid('root'));
// export default app 
// i am not sure you usage but since you already rendered it so i assume this line is not needed

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