Dynamically add global constant in webpack

I'm trying to add a global constant to my project. For this I use webpack.DefinePlugin. This works if I add one in the module.exports. I fail to do this conditionally however. In the config below I'm able to use the __VERSION__ constant in my module after declaring it like so: declare var __VERSION__: string;. If I try to use __VERSION2__ or __VERSION3__ I get an error in the console ReferenceError: __VERSION3__ is not defined. If my understanding is correct this should have been replaced. Does this mean that the conditional part is not executed or not executed correctly? How can I debug this? Or even better, how can I fix this?

Note: the intention is to switch a url based on development or production build.

The current project can be found here on github

webpack.config.js:

// Based on https://github.com/microsoft/typescript-vue-starter#adding-webpackvar path = require('path')
var webpack = require('webpack')

module.exports = {
    mode: 'development',
  entry: './src/ts/main.ts',
  output: {
    path: path.resolve(__dirname, './dist'),
    publicPath: '/dist/',
    filename: 'build.js'
  },
  module: {
    rules: [
      {
        test: /\.vue$/,
        loader: 'vue-loader',
        options: {
          loaders: {
            // Since sass-loader (weirdly) has SCSS as its default parse mode, we map// the "scss" and "sass" values for the lang attribute to the right configs here.// other preprocessors should work out of the box, no loader config like this necessary.'scss': 'vue-style-loader!css-loader!sass-loader',
            'sass': 'vue-style-loader!css-loader!sass-loader?indentedSyntax',
          }
          // other vue-loader options go here
        }
      },
      {
        test: /\.tsx?$/,
        loader: 'ts-loader',
        exclude: /node_modules/,
        options: {
          appendTsSuffixTo: [/\.vue$/],
        }
      },
      {
        test: /\.(png|jpg|gif|svg)$/,
        loader: 'file-loader',
        options: {
          name: '[name].[ext]?[hash]'
        }
      },
      {
        test: /\.css$/,
        use: ['style-loader', 'css-loader']
        }
    ]
  },
  resolve: {
    extensions: ['.ts', '.js', '.vue', '.json'],
    alias: {
      'vue$': 'vue/dist/vue.esm.js'
    }
  },
  plugins: [ 
    new webpack.DefinePlugin({
        __VERSION__: JSON.stringify('1.0.0.' + Date.now())
    })],
  devServer: {
    historyApiFallback: true,
    noInfo: true
  },
  performance: {
    hints: false
  },
  devtool: 'source-map'
}

if (process.env.NODE_ENV === 'production') {
  module.exports.devtool = 'source-map'// http://vue-loader.vuejs.org/en/workflow/production.htmlmodule.exports.plugins = (module.exports.plugins || []).concat([
    new webpack.DefinePlugin({
      'process.env': {
        NODE_ENV: '"production"'
      }
    }),
    new webpack.DefinePlugin({
        __IN_DEBUG__: JSON.stringify(false),
        __VERSION2__: JSON.stringify('1.0.0.' + Date.now())
    }),
    new webpack.optimize.UglifyJsPlugin({
      sourceMap: true,
      compress: {
        warnings: false
      }
    }),
    new webpack.LoaderOptionsPlugin({
      minimize: true
    })
  ])
}
else if(process.env.NODE_ENV === 'development')
{
    module.exports.plugins.push(
        new webpack.DefinePlugin({
            __VERSION3__: JSON.stringify('1.0.0.' + Date.now())
        }));
}