From the New File dialog, select Web > Empty JS file or Web > TypeScript file. Give it a name and then choose New:
Type inference – The type of an object is figured out by the surrounding code context. For more information, see Visual Studio's section on IntelliSense based on type inference.
JSDoc – There are times when type inference doesn't provide the correct type information. In these cases, the type information can be provided explicitly by JSDoc annotations. For more information, see Visual Studio's section on IntelliSense based on JSDoc
TypeScript declaration files –