title: Environment variables in TypeScript
body: <p>If we have some environment variables which are present in the environment in  which the compiled JavaScript is going to run, how we can mention those variables in Typescript code ?</p>
  
  <p>In TypeScript varaibles cannot be used without being declared. If it is declared like <code>let env_varaible;</code>, it become <code>var env_variable;</code> which eventually overridethe actual varaible. What is the solution for this?</p>