ReferenceError: React is not defined

Question

浏览器报错ReferenceError: React is not defined

//login.js
import React from 'react';
import { render } from "react-dom";


render(
    <h1>test</h1>,
    document.getElementById('root')
);

//webpack.config.js
                test: /\.js$/,
                exclude: path.resolve(__dirname, "node_modules"),
                include: path.resolve(__dirname, "public/src"),
                loader: "babel-loader",
                query: { //babel参数配置
                    "presets": ["env", "react"]
                }
              ...
              new webpack.ProvidePlugin({
                'React': 'react',
              })

生成的js也包括了react，但是还是报错