No, JavaScript is not valid TypeScript. This might be a silly example but there are dozens of similar, small JavaScript programs that are not legal TypeScript

No, JavaScript is not valid TypeScript. This might be a silly example but there are dozens of similar, small JavaScript programs that are not legal TypeScript (for good reason!). http://crystae.net/2015/01/22/typescript-is-not-a-superset-of-javascript/ http://crystae.net/2015/01/22/typescript-is-not-a-superset-o... Try running jQuery's source through the TypeScript compiler some time.