wepack配置了 webpack-dev-server ,貌似也监听到了文件的变化，但是bundle.js中没有跟着刷新，怎么回事？
目录如下

package.json

请输入代码

{
"name": "webgldeom",
"version": "1.0.0",
"description": "use threejs demo",
"main": "./app/index.js",
"scripts": {

"webpack": "node node_modules/webpack/bin/webpack.js",
"start": "node node_modules/webpack-dev-server/bin/webpack-dev-server.js --inline --port 8080 --progress",
"build": "node node_modules/webpack/bin/webpack.js -p --devtool hidden-module-source-map"

},
"author": "bin.yang",
"license": "ISC",
"devDependencies": {

"webpack": "^1.14.0",
"webpack-dev-server": "^1.16.2"

}

配置文件：webpack.config.js如下

var webpack = require('webpack');

    module.exports = {
        devtool: 'source-map',
    
        //页面入口文件配置
        entry:'./app/index.js',
        
        //入口文件输出配置
        output: {
            filename: 'bundle.js',
            path: './build',
        },
        resolve: {
            root: './node_modules',
            extensions: ['', '.js', '.json', '.scss'],
        }
    };

index.html