#typescript

We recently started a new project and decided to use TypeScript along with Angular 1.5. Angular 1.5 introduces a new abstraction called a “component” which closely resembles Angular 2’s component based approach. Surprisingly, there isn’t a lot of simple TypeScript sample code available for Angular 1.5 so I decided to throw something together in case anyone else is looking. The code is available at https://github.com/Setfive/ng_typescript_starter and a live demo of it is running at http://code.setfive.com/ng_typescript_starter.

So what are some standouts with TypeScript and Angular 1.5?

  • The 1 way bindings components introduce are easier to reason about but having to explicitly add functions for “outputs” does add some verbosity
  • Related to that, there’s a fair amount of boilerplate to create a single component since you have to define 2 classes
  • Dropping $scope in favor of automatically binding the controller object to $ctrl in templates is great – especially with TypeScript classes
  • Related to that, without $scope for events it’s unclear when it’s appropriate to use $rootScope for an event bus
  • You can write typesafe code for almost all of your controller business logic
  • It’s really unfortunate the TypeScript compiler can’t typecheck your Angular templates
  • Using the $inject annotation with component classes looks “right” versus the “array like” syntax
  • You need to be somewhat cognizant of matching your @types annotations with the correct version of the library you’re using
  • Using components with ui-router makes it fairly difficult to communicate between sibling views

Anyway, beyond fighting with build tools to convert a TypeScript project into usable JavaScript the language part has been great to work with. We ended up using Browserify with tsify but it was pretty frustrating to get it working. I might of missed something but it seems like I needed tsify available in a separate node_modules directory from the project source. The demo app is setup this way for that reason.

As always, questions and comments are welcome!

Posted In: AngularJS, Javascript

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Over the past few day we’ve been evaluating using Angular 1.x vs. Angular 2 for a new project on which in the past we would have used Angular 1.x without much debate. However, with release of Angular 2 around the corner we decided to evaluate what starting a project with Angular 2 would involve. As we started digging in it became clear that using Angular 2 without programming in TypeScript would be technically possible but painful to put it lightly. Because of the tight timeline of the project we decided that was too large of a technical risk so we decided to move forward with 1.x. But I decided to spend some time looking at TypeScript anyway, for science. I didn’t have anything substantial to write but needed to hammer out a quick HTML scraper so I decided to whip it up in TypeScript.

Getting started with TypeScript is easy you just use npm to install the tranpiler and you’re off to the races. As I started experimenting, I fired up PhpStorm 10+ and was thrilled to learn it has good TypeScript support out of the box (thanks JetBrains!). The scraper I was writing is pretty simple – make a series of HTTP requests, extract some elements out of the HTML via CSS selectors, and write the results out to a CSV. Coming from a JavaScript background, jumping right into TypeScript was easy enough since TypeScripts’ syntax is basically ES2015 with additional Java or C# like type declarations. The scraper is less than 100 lines so I didn’t get a great sense of what programming with TypeScript would be like but here are some initial takeaways.

It’s easy to end up missing out on the benefits. Since TypeScript is a superset of JavaScript you’re free to ignore all the type features and write TypeScript that is basically ES2015. Combine that with the fact that the tsc transpiler will produce JavaScript even with type errors and you can quickly find yourself not enjoying any of the benefits TypeScripts introduces. This issue isn’t unique to TypeScript since you can famously write You Can Write FORTRAN in any Language but I think since its a superset of an existing, popular langue the temptation is much stronger.

Discovering functionality in modules is easier. In order to properly interface with nodejs modules you’ll need to grab type definitions from somewhere like DefinitelyTyped. The definition files are similar to “.h” files from C++, code stubs that just provide function type signatures to TypeScript. An awesome benefit of this is that it’s much easier to “discover” the functionality of nodejs modules by looking at how the functions transform data between types. It also makes it much easier to figure out the parameters of a callback without having to dig into docs or code.

Typed generics will unequivocally reduce bugs. I’d bet a beer or two that most web developers spend the majority of their day writing code that deals with lists. Creating them, filtering them, transforming them, etc. Unfortunately, most of the popular scripting languages don’t have support for typed generics and specifically enforcing uniform types within arrays. Specifically with JavaScript, it’s pretty easy to end up at a point where you’re unsure of what’s contained in a list and moreover if the objects within it share any of the same properties. Because of this, I think TypeScript’s typed generics will cut down on bugs almost immediately.

TypeScript is definitely interesting and it’s tight coupling to Angular 2 only bolsters how useful it’ll be in the future. Next up, I’d be interested in building something more substantial with both a client and server component and hopefully share some of the same code on both.

As always, questions and comments are more than welcome!

Posted In: Javascript

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