Ask a Ninja: Do I need Typescript?

If the .Net Ninja would have been asked this question, this would be the answer:

A few days ago Anders Hejlsberg showed a new thing currently brewing in the Microsoft labs: TypeScript.

TypeScript is:

  • JavaScript
  • + some (optional) language extensions
  • + a Compiler (more of a extractor, in fact), that removes the extensions and throws out vanilla JavaScript

The compiler itself is also written in TypeScript, so it can be compiled down to pure JavaScript and run wherever JavaScript will run too.

So, now that we know that TypeScript is a mere superset on top of normal JavaScript – what is in these additions that could be interesting?

  • Strong typing
  • Classes
  • Interfaces
  • Simple inheritance
  • Modules

Well, in fact that’s pretty much it. With some annotations in Pascal-Style (that is, colon + type identifier) you can define that a specific variable, function argument or function return value needs to be of a certain type.

var testFunc = function(arg1: string) { return "Argument was: " + arg1; };

Now the TypeScript compiler knows that only strings should be passed into the function assigned to testFunc. And it can infer from the input argument and the operation within this function, that the return value must also be a string. Now, when you try to pass i.e. a number into this function, the compiler will warn you about this, and the same goes when you want to add a number to the return value of this function.

Actually not only the compiler, but also the full IDE support in VisualStudio will highlight this as a potential problem. Also the IDE is so smart to restrict your Intellisense autocompletion to valid types only. These simple annotations are a big player in making JavaScript a bit safer when working with different types.

TypeScript also allows you, to annotate external libraries like jQuery, Prototype, Qooxdoo etc., and it comes with some of them already pre-annotated to give you a head-start.

The other interesting thing is that the way of modularizing the scripts sticks strongly to what is currently proposed to become the next EcmaScript 6 standard. Of course this is only a specification draft by now, and will take some time to be finalized, and it is not sure if the specs will stay this way forever, but this way it is very likely that what you learn with TypeScript can be used in the future for vanilla JavaScript too.

Ask the Ninja: “So, do I *need* TypeScript?
Ninja says:
Need as in totally and absolutely required? Of course no.

TypeScript is an addition to JavaScript that, if used correctly, can help you avoid some nasty bugs. And only, if you are a fan of strong typing and come to JavaScript from other strong typed languages on the .NET or Java Platform or even from Delphi. Then TypeScript is targeted for you!

When you already are a happy JavaScript developer and make use of the dynamic typing features of the language, switch prototype chains on your objects as required and love applying and removing things at run-time, then there is nothing in TypeScript for you.

Author: Sebastian Gingter

Software Engineer at Thinktecture, Fulltime geek, loving father & husband, always learning.