Well, TypeScript is great but there are some disadvantages as well.

• TypeScript is just another way to write JavaScript. It doesn’t fix the problems of JavaScript. It just creates an illusion that it does.
• One more tool to learn.
• TypeScript has dependency on type definition files, if you wish to use any existing JavaScript libraries.
• Quality of type definition files is a CONCERN as how can you be sure the DEFINITIONS are correct?
• Frequent releases of new versions JavaScript library is also a pain area. Because if their type definition files are not updated then you can’t use them instantly.
• In order to run the APPLICATION in the browser, a compile step is required to transform TypeScript into JavaScript.
• WEB developers are using JavaScript from decades and TypeScript doesn’t bring ANYTHING new.
• To use any third party library, definition file is you need. And not all the third party library have definition file available.

Well, TypeScript is great but there are some disadvantages as well.