title: How lexer and parser got implemented?
body: <p>I was discovering how programming languages like TypeScript is implemented so I went to the Github repository. </p>
  
  <p>In the language source <code>/src/compiler</code> I found files like <strong>scanner.ts</strong> and <strong>parser.ts</strong> so the code inside these files is TypeScript code.</p>
  
  <p>I cannot understand how the language is implementing itself?
  I guess there is some missing pieces I do not know.
  Please mention any terminology that might be helpful.</p>