Подскажите как в AJAX запросе получить файл

import React from "react"; 
import PageOne from "./pageone"; 
 
 
class Main extends React.Component { 
	constructor(props){ 
		super(props); 
			this.state = { 
					WeatherObj:null 
			} 
		} 
	componentWillMount(){ 
		this.getWeather(); 
	} 
	getWeather(){ 
		let req = new XMLHttpRequest(); 
		req.onload = () => { 
			this.setState({WeatherObj:req.response}); 
		} 
		req.open("GET", "auto.json", true); 
		req.responseType = "json"; 
		req.send(); 
	} 
 
 
	render() {		 
		let weather = this.state.WeatherObj; 
		console.log(weather); 
      	return( 
      		<button>Запустить</button> 
      	) 
   	 
	 
 
	} 
 
} 
export default Main;

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script> 
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>