I’m learning TypeScript

A couple of months back, I talked about how I was trying to learn TypeScript. Well, I’m really learning TypeScript and getting my hands dirty. One of the things that made this a little easier for me was that the latest official 1.5 release supports more ES6 features, such as ES6 modules. This means that instead of writing import foo = require(‘foo’);, I can just write import foo from ‘foo’; just like I would in ES6. That is pretty cool and keeps my head in the same zone as I’m normally used to.

The other really cool part of 1.5 that should be of interest to people using the ArcGIS JS API, is the official support for AMD dependencies. You can read more about this in this awesome Sitepen blog post. This allows you to use loader plugins and easily add AMD modules to your app. Something like this:

As you can see, I load my AMD modules via the amd-dependency tag, then use declare var module:any to be able to use it in my code. If you look at this, aside from the dependency tags and typings, this looks just almost identical to ES6. The dojo definition files I’m currently using complain about not naming my dojoDeclare, but I think if I switched to a different one, this might go away. That’s another one you may notice. declare is a keyword in TypeScript, so you’ll need to refer to it as dojoDeclare or something else in your code. As of right now, you still need *dojo/_base/declare** for some bits since TypeScript doesn’t support multiple inheritance. I’m sure this will be addressed via some mechanism in the future.

If you are only going to extend a single module, you can use a TypeScript class.

In this case, I am only extending a single class, which is defined in the dojo TypeScript definition file. This is a lot cleaner to do.

I’m still learning best practices when using Interfaces and also when to best use export foo or export = foo or export default foo and to import them into modules.

I’ve put up a demo app here.

The SitePen blog has been a really good resource for TypeScript info and the wiki has all the latest info. SitePen has really been pushing a lot of TypeScript stuff as Dojo2 will be all TypeScript. Here’s a cool recent video from a SitePen employee talking about TypeScript.

I’m a big fan of ES6 and if I can get some extra developer boosts from using TS, with typings and interfaces, I may just be doing my apps in TS, if for nothing more than experimentation, which is what I do. I know there are folks out there using TypeScript right now for their ArcGIS JS development, so I’d love to hear from you on your experience and any tips and tricks you may have. In the meantime, I’ll keep on learning.