How to specify JS-only output path in Webpack?

Question

webpack

webpack.config.js

module.exports = {
...
    entry: {
        'js/main' : './main',
        'js/common' : './common' //CommonChunksPlugin
    },
...
}

if(Settings.jsUglify){
    module.exports.plugins.push(
        new webpack.optimize.UglifyJsPlugin({
            compress : {
                warnings : false,
                drop_console: true,
                unsafe: true
            }
        })
    );
}

The problem is this: when building with CommonChunkPlugin, a js file variable is created, i.e. my entry config creates an output variable:
var js/main = ...
This is a js bug and uglify can't minify the code.
If my entry looks like this, then there is no problem:

module.exports = {
...
    entry: {
        'main' : './main',
        'common' : './common' //CommonChunksPlugin
    },
...

How can I set a separate directory for the collected JS files?