Sample gulp config task for typescript using gulp ng-constant, creates a Angular constant typescript file

config.js

'use strict';
var gulp = require('gulp');
var $ = require('gulp-load-plugins')();

gulp.task('config', function () {
  var config = require('../config.json'),
      envConfig = config.development;

  [process.env.NODE_ENV === 'production' ? 'production' : 'development']
  if(process.env.NODE_ENV === 'production'){
    console.log('loading production config');
    envConfig = config.production;
  } else{
    console.log('loading dev config');
  }

  return $.ngConstant({
        constants: envConfig,
        templatePath: 'constant.tpl.ejs',
        stream: true
      })
    .pipe($.rename('config.ts'))
    .pipe(gulp.dest('src/app/'));
});

config.json

{
  "development": {
    "apiBase": "http://localhost:3000/api"
  },
  "production": {
    "apiBase": "https:/someurl.net/api"
  }
}

constant.tpl.ejs

export interface IConstants {<% constants.forEach(function(constant) {%>
    <%= constant.name.replace(/"/g, "'") %>: string;<% }) %>
}

export default {<% constants.forEach(function(constant) {%>
    <%= constant.name.replace(/"/g, "'") %>: <%= constant.value.replace(/"/g, "'")%>,<% }) %>
};

export var Constants = {<% constants.forEach(function(constant) {%>
    <%= constant.name.replace(/"/g, "'") %>: <%= constant.value.replace(/"/g, "'")%>,<% }) %>
};

index.module.ts

import Constants from './config';

module appName {
  'use strict';

  angular.module('appName', [
    'ngAnimate',
    'ngCookies',
    'ngTouch',
    'ngSanitize',
    'ngMessages',
    'ngAria',
    'ui.router',
    'ngMaterial',
    'ngResource',
    'formly'
    ])
    .constant('constants', Constants)
  }

main.controller.ts

import { Constants } from './config';

export class MainController {
  public apiBase: string;

  /* @ngInject */
  constructor (constants: Constants) {
    this.apiBase = constants.apiBase
  }
}