Around two months ago I started a new pet project. As always, I built it partly to solve a problem, and partly to learn some new language or technology. The problem I wanted to solve was showing images and maps to players when playing table-top role-playing games (and, while at it, manage my music from the same place). The language and technology were TypeScript and to a lesser extent ES2015. As always, I learned some things I didn’t quite expect or plan, like HTML drag-and-drop, Riot, a bit more Flexbox, and some more canvas image processing. The result is the first public version of Lyre, my program to help storytellers integrate music and images into their stories (especially useful for semi-improvised or interactive stories).

But the reason for this post is to talk a little bit about the technology. I admit that I haven’t really studied TypeScript thoroughly (I mostly learned bits and pieces while programming), but I think I like it to the point that it might become my front-end language of choice when I cannot use ClojureScript or similar.

So, what’s so great about it? Essentially, it’s ES2015 with optional types. The bad thing is that it needs special incantations to be able to use regular JavaScript modules, and in most cases you don’t have types defined for non-TS modules so you end up with type any for everything. The good thing is that it’s extremely familiar for people who know ES2015, because it’s almost the same, and that of course you can specify types wherever you want to. I am not the biggest fan of static types, but after trying it I think I really like the idea of optional types. Moreover, types in TypeScript are relatively open and feel like they fit very well in the JavaScript ecosystem. Two examples:

  1. Apart from enums, you can create union types that eg. are as simple as a choice between two strings, like type Mode = "off" | "on".
  2. Interfaces can be used to specify the properties, not just methods, that should be available in an object. Among other things, it’s possible to specify that an object should have certain specified properties plus any number of extra properties as long as their values are of a given type.

They have other interesting features, like union and intersection types, type guards for functions, decorators, generics and others things. I haven’t really used most of those, but I realised that I liked TypeScript when I was writing some JavaScript and found myself missing the optional types.

For actual editing I’m of course using Emacs, in this case with TIDE. Although the refactoring capabilities are very limited, the rest worked quite well and I’m very happy with it.

The other bigger thing I learned was Riot. Which, sadly, I didn’t like as much: I found it very confusing at times (what does this point to in the templates? it seems to depend on the nesting level of the ifs or loops), ended up with lots of rebinding of methods so they could be safely passed around in templates, and generally felt that I spent too much time fighting with it rather than writing my application. Now, some of these problems might have been caused by Riot-TS and not Riot itself, but still the experience wasn’t that great and I don’t expect to use it again in the future. Again, bear in mind that I mostly tried to learn on the go, so maybe I was doing everything wrong :-)

In conclusion, I love these projects because I end up with something useful and because I always learn a bunch of things. In this case in particular, I even learned a language that positively surprised me, even if I’m not a big fan of static typing. Again, if you want to have a look at the result, you can learn about Lyre and download the code from GitHub.