Add markdown list item on enter to textarea

App.js

import React, { Component } from 'react';
import './App.css';

class App extends Component {

  constructor(props) {
    super(props);
    this.state = {
      text: '- asda'
    };
    this.myRef = React.createRef();
    this.handleChange = this.handleChange.bind(this);
    this.handleKeyDown = this.handleKeyDown.bind(this);
  }

  handleChange(e) {
    this.setState({ text: e.target.value });
  }

  handleKeyDown(e) {
    if (e.keyCode === 13) {
      
      let cursorPos = e.target.selectionStart;
      let val = e.target.value;
      let textBefore = val.substring(0,  cursorPos );
      let textAfter  = val.substring( cursorPos, val.length );
      let lineBefore = textBefore.split('\n').pop();
      let isMatch = lineBefore.match(/-\s[a-zA-Z]+/g);

      if (isMatch != null) {
        e.preventDefault();
        let newVal = textBefore + '\n- ' + textAfter.trimRight();
        this.setState({ text: newVal });
        setTimeout(() => {
          this.myRef.current.setSelectionRange(cursorPos+3, cursorPos+3);
        }, 0);
        return false;
      } 

      if (lineBefore == '- ') {
        e.preventDefault();
        let clipped = textBefore.substring(0, textBefore.length - 3);
        let newVal = clipped + '\n\n' + textAfter.trimRight();
        this.setState({ text: newVal });
        setTimeout(() => {
          this.myRef.current.setSelectionRange(cursorPos+3, cursorPos+3);
        }, 0);
        return false;
      }

    }
  }

  render() {
    return (
      <textarea ref={this.myRef} className="App" value={this.state.text} onChange={this.handleChange} onKeyDown={this.handleKeyDown} />
    );
  }

}

export default App;