For anyone working iteratively using webpack --watch: First do npm install node-notifier --save-dev and then put this into webpack.config.js:

const notifier = require('node-notifier');
  ...
  plugins: [
    function() {
      this.plugin("done", function(stats) {
          if (stats.hasErrors()) {
            notifier.notify('Error');
          } else {
            notifier.notify('Ok!');
          }
      });
    }
  ]
  ...

Now a notifier will appear each time the build passes (or fails) so you don't need to look at the terminal each time. Nice for keeping the flow!