fxgk-mobile-app/config/webpack.config.js

// Set the `ENV` global variable to be used in the app.
var path = require('path');
var webpack = require('webpack');

var projectRootDir = process.env.IONIC_ROOT_DIR;
var appScriptsDir = process.env.IONIC_APP_SCRIPTS_DIR;

var env = process.env.NODE_ENV || 'dev';

var config = require(path.join(appScriptsDir, 'config', 'webpack.config.js'));

var envVars;

if(process.env.IONIC_ENV === 'prod'){
  config = config["prod"];
} else {
  config = config["dev"];
}

try {
  envVars = require(path.join(projectRootDir,'src', 'environments', env + '.json'));
} catch(e) {
  envVars = {};
}

config.plugins = config.plugins || [];
config.plugins.push(
  new webpack.DefinePlugin({
    ENV: Object.assign(envVars, {
      environment: JSON.stringify(env.trim())
    })
  })
);

if(env === 'prod') {
  // This helps ensure the builds are consistent if source hasn't changed:
  config.plugins.push(new webpack.optimize.OccurrenceOrderPlugin());
}

module.exports = config;