How to configure and run webpack from .js file instead of webpack.config

i am creating dynamicly generated webpack module base on user input.

Standard static way where you specifi folder or files in config and run webpack on it with babel-loader works correctly.

var path = require('path');

var webpack = require('webpack');
var CopyWebpackPlugin = require('copy-webpack-plugin');

var dir_js = path.resolve(__dirname, 'js');
var dir_html = path.resolve(__dirname, 'html');
var dir_build = path.resolve(__dirname, 'build');

module.exports = {
    entry: path.resolve(dir_js, 'main.js'),
    output: {
        path: dir_build,
        filename: 'bundle.js'
    },
    devServer: {
        contentBase: dir_build,
    },
    module: {
        loaders: [
            {
                loader: 'babel-loader',
                test: dir_js,
            }
        ]
    },
    plugins: [
        // Simply copies the files over
        new CopyWebpackPlugin([
            { from: dir_html } // to: output.path
        ]),
        // Avoid publishing files when compilation fails
        new webpack.NoErrorsPlugin()
    ],
    stats: {
        // Nice colored output
        colors: true
    },
    // Create Sourcemaps for the bundle
    devtool: 'source-map',
};

However if I want to make module dynamicly i cant use static config file. So i google a bit how could I directly call webpack from JS file with some specific configuration. I found THIS

Where there is option to call:

var webpack = require("webpack");    
// returns a Compiler instance
webpack({
    // configuration
}, function(err, stats) {
    // ...
});

So i create something really simple index.js:

var webpack = require('webpack');
webpack({
    entry: './main.js',
    output: {
        filename: 'bundle.js'
    }
}, function(err, stats) {
    // console.log(stats);
    console.log(err);
});

Unfortunately nothing happend when i call this file via node index.js, even console.log(err) output is null From this point i didnt find anything else usefull.

So i hope if here is anyone who have experience with that and can advise me what I'm doing wrong. Or alternativly give me advise whats the other way how to create it