Allow using different configuration files in order to instrument the build

ionic2-env-conf.md

ExtendedDefinePlugin will replace ENV variables by their configuration value. Uglify will remove dead code.

1. Copy and modify webpack.config.js

// EDIT by Jean DAT
// Custom code in order to load different configuration files based on context (targeted environment).
// In a configuration file, I store things like the API url to use, etc.
var ExtendedDefinePlugin = require('extended-define-webpack-plugin');
var optimist = require('optimist');
var argv = optimist.argv;
if (!argv.env) argv.env = process.env.IONIC_ENV;
var envParameters = require('../env/' + argv.env + '.js');
envParameters.prod = argv.env === 'prod';
envParameters.dev = argv.env === 'dev';
console.log('Using env parameters (' + argv.env + '):', JSON.stringify(envParameters, null, '    '));
// END EDIT

module.exports = {

...

plugins: [
    // EDIT by Jean DAT
    new ExtendedDefinePlugin({ENV: envParameters}),
    // END EDIT
    ionicWebpackFactory.getIonicEnvironmentPlugin()
  ],
  
...

2. Create one js file per environment inside env folder

// ./env/dev.js
module.exports = {
  apiUrl: 'http://example.com/api/dev'
};

3. Declare custom webpack config file inside package.json

4. Declare ENV variable inside declaration.d.ts

declare let ENV: any;

5. Use in code

if(ENV.dev) console.log('## DEV ##');

...

export class Api {
  url: string = ENV.apiUrl;