gulpfile.js

var gulp = require("gulp");
var gutil = require("gulp-util");
var webpack = require("webpack");
var webpackConfig = require("./webpack.config.js");

gulp.task("build", ["webpack:build"]);

gulp.task("webpack:build", function (callback) {
  // modify some webpack config options
  var myConfig = Object.create(webpackConfig);
  myConfig.plugins = myConfig.plugins.concat(
    new webpack.DefinePlugin({
      "process.env": {
        // This has effect on the react lib size
        "NODE_ENV": JSON.stringify("production")
      }
    }),
    new webpack.optimize.UglifyJsPlugin({
      compress: {
        warnings: true
      }
    })
  );

  // run webpack
  webpack(myConfig, function (err, stats) {
    if (err) throw new gutil.PluginError("webpack:build", err);
    gutil.log("[webpack:build]", stats.toString({
      colors: true
    }));
    callback();
  });
});