// ...
_onClick = (e) => {
    this.onChange(RichUtils.toggleInlineStyle(this.state.editorState, e.target.name));
}
render() {
    const styles = ['BOLD', 'ITALIC', 'UNDERLINE', 'CODE'];
    const buttons = styles.map(style => {
      return <button key={style} onClick={this._onClick} name={style}>{style}</button>
    })
    return (
      <div className="App">
        <h1>My Editor</h1>
        <div className='toolbar'>
          {buttons}
        </div>
        //...
      </div>
     )
};