react/fixtures/fiber-debugger/src/Editor.js

import React, {Component} from 'react';

class Editor extends Component {
  constructor(props) {
    super(props);
    this.state = {
      code: props.code,
    };
  }

  render() {
    return (
      <div
        style={{
          height: '100%',
          width: '100%',
        }}>
        <textarea
          value={this.state.code}
          onChange={e => this.setState({code: e.target.value})}
          style={{
            height: '80%',
            width: '100%',
            fontSize: '15px',
          }}
        />
        <div style={{height: '20%', textAlign: 'center'}}>
          <button
            onClick={() => this.props.onClose(this.state.code)}
            style={{fontSize: 'large'}}>
            Run
          </button>
        </div>
      </div>
    );
  }
}

export default Editor;