title: Difference between UglifyjsWebpackPlugin and UglifyJsPlugin
body: <p>I am slightly confused about the difference between UglifyjsWebpackPlugin and UglifyJsPlugin.
  Webpack 2 documentation talks about both of them in separate pages - 
  1. <a href="https://webpack.js.org/guides/production-build/#minification" rel="nofollow noreferrer">https://webpack.js.org/guides/production-build/#minification</a>
  2. <a href="https://webpack.js.org/plugins/uglifyjs-webpack-plugin/" rel="nofollow noreferrer">https://webpack.js.org/plugins/uglifyjs-webpack-plugin/</a></p>
  
  <p>Second link also talks about dependency on git://github.com/mishoo/UglifyJS2#harmony for ES6 minification target. </p>
  
  <p>Which one should I use in production (react app).</p>