title: Optional strongly typed compilers
body: <p>Is there any language/framework for generating JavaScript with support for optional strongly typed code?</p>
  
  <p>Something that would allow writing code as not strongly typed, but with an option to run checks and/or compile a report about where it would fail if it were strongly typed.</p>
  
  <p>As a side question, is it possible to make TypeScript turn off its strongly typed enforcement?</p>