when I use webpack about css hot-loading too slow

Q: Without 'extract-text-webpack-plugin'. I change css files, each modification style will be updated in the same time, but the screen a few seconds is flash . the reason is that,the style is write within js.

After,I use 'extract-text-webpack-plugin', the screen do not flicker and the style do not update in the same time. I tried long time,but anything harvest, so I want you guys help me.

look this

enter image description here