title: What is best and recommended way of using constants in Angular 5
body: <p>I have a Angular 5 application where I want to use </p>
  
  <ul>
  <li>a. application level constants </li>
  <li>b. Module level constants</li>
  </ul>
  
  <p>I know we can use DI (Injection Token), or Services to use constants, or create a global.ts file with all constants and then access them anywhere. </p>
  
  <p>I wanted to understand what is the best and recommended way of doing this.</p>