index.js

// @flow
import * as React from "react";
import { Editor, EditorState } from "draft-js";

type Props = {
  onChangeText?: (text: string) => void
};

type State = {
  editorState: EditorState
};

export default class CustomEditor extends React.Component<Props, State> {
  static defaultProps = {
    onChangeText: () => {}
  };

  state = { editorState: EditorState.createEmpty() };

  onChange = (editorState: EditorState) => {
    const { onChangeText } = this.props;
    const text = editorState.getCurrentContent().getPlainText();

    this.setState({ editorState }, () => {
      if (onChangeText) onChangeText(text);
    });
  };

  render() {
    const { editorState } = this.state;
    return <Editor editorState={editorState} onChange={this.onChange} />;
  }
}