试试这么写， 在我工程里好用的：

module: {
    rules: [
      {
        test: /\.less$/,
        use: Extract.extract({fallbackLoader: 'style-loader', loader: ["css-loader", "less-loader"]})
      },
      {test: require.resolve("jquery"), use: "expose-loader?$"},
      {test: require.resolve("jquery"), use: "expose-loader?jQuery"},
      {test: require.resolve("react"), use: "expose-loader?React"},
      {test: require.resolve("react-dom"), use: "expose-loader?ReactDOM"},
      {test: require.resolve("underscore"), use: "expose-loader?_"}
    ]
}

我的也是webpack2 这样写没问题呢：

{
    // 得到jquery模块的绝对路径
    test: require.resolve("jquery"),
    // 将jquery绑定为window.jQuery 和 window.$       
    loader: "expose-loader?jQuery!expose-loader?$"
},