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Microsoft Announces TypeScript 3.0 (neowin.net)
Microsoft released version 3.0 of TypeScript, which Microsoft describes as an "extension" of JavaScript "that aims to bring static types to modern JavaScript." Quoting Microsoft's Developer Tools blog:
The TypeScript compiler reads in TypeScript code, which has things like type declarations and type annotations, and emits clean readable JavaScript with those constructs transformed and removed. That code runs in any ECMAScript runtime like your favorite browsers and Node.js. At its core, this experience means analyzing your code to catch things like bugs and typos before your users run into them; but it brings more than that. Thanks to all that information and analysis TypeScript can provide a better authoring experience, providing code completion and navigation features like Find all References, Go to Definition, and Rename in your favorite editor.
Neowin reports: With any major version release, it is not unexpected for breaking changes to be introduced and that's certainly the case for TypeScript 3.0. One obvious change is that with "unknown" becoming a new type, it is now a reserved type name and can no longer be used in type declarations. Otherwise, there's a range of API breaking changes due to a number of functions and internal methods being deprecated or being made internal.
On the plus side, TypeScript 3.0 reportedly has improved error messages, along with project references that let TypeScript projects have dependencies on other TypeScript projects.
Neowin reports: With any major version release, it is not unexpected for breaking changes to be introduced and that's certainly the case for TypeScript 3.0. One obvious change is that with "unknown" becoming a new type, it is now a reserved type name and can no longer be used in type declarations. Otherwise, there's a range of API breaking changes due to a number of functions and internal methods being deprecated or being made internal.
On the plus side, TypeScript 3.0 reportedly has improved error messages, along with project references that let TypeScript projects have dependencies on other TypeScript projects.
TypeScript compiles to JavaScript while at the same time you can mix it with pure JavaScript. This makes it easy to add TypeScript to an existing project. The fact TypeScript is based off of JS means it is easy for JS developers to learn it. Plus, you have something JS does not have: consistency. Want to use the class keyword in JS? You need to make sure all your supported browsers have implemented it and it'll work. In TypeScript you have several different compile targets depending on your lowest common denominator of JS version support you need.
TypeScript is a good solution to all the problems JS has, the most serious one I think being the lack of compile-type errors, pushing them to more difficult to find and fix runtime errors and logical errors.