webpack ^4.0.1 版本的webpack.config.js配置

var path = require("path");
module.exports = {
entry:'./app/index.js',
output:{
filename:'index.js',
path:path.resolve(__dirname,'dist'),
publicPath:'temp/'                       //公共路径，从内存中读取
},
devServer:{
contentBase:'./',
host:'localhost',
compress:true,
port:1818
},
module:{
rules:[
{
test:/\.js$/,
exclude:/node_modules/,
loader:'babel-loader',
options:{
presets:["es2015","react"]
}
}
]
}
}