TypeScript

Posted by Andy Armstrong on 7/6/2016

Intro

TypeScript is an open source compiled superset language of Javascript maintained by Microsoft. Introduced in 2012 after several internal iterations, the project was born out of the desire to add some variable typing to Javascript. Hence, TypeScript.
While you may first recoil at the idea of another transpiled javascript library, let me explain some of the great features and speed increases you can get by including it in your workflow and you might change your mind.

How it Works

TypeScript is just a superset of JS that compiles to ES3, ES5 or ES6. Think of this as a higher level language that normalizes the features of ES5 & ES6 into a version compatible with your target language and polyfills missing features.
This means, if you are compiling to ES3, TS will turn your fancy ES6 class into the syntactic sugar required to replicate it in ES3. Also, it will do it better than you.

Why TypeScript is a good thing: you can have ES6 features, now

ES6 compatibility is woefully lacking for most browsers found in the wild, which is definitely appealing if you want to use some of those cool features you hear about… especially the ones that most people gripe about the lack of in JS (classes and inheritance) when compared to most other OOP languages.
Classes and Modules are now available to you, and down compiled . You can use the super cool (and often confusing on your first encounter) “arrow” functions notation for your Anonymous Functions. Rest functions where you can finally make your functions as flexible as you want them.
When you let TypeScript transpile your code you can have all of those amazing ES6 features with your current user base’s browsers! Yes, even Safari!

Why TypeScript is a good thing: You get type hints, type checking at compile time

Loose typing has always been a gripe of higher level languages like PHP and Javascript. At its core, the argument really comes down to keeping your code clean and safe by asserting you pass and ask for the correct types of variables. If your reading this, and enjoying it, I’m sure you have encountered the terrible spiral of type juggling and the concept of ‘falsy’ when looking for an optional variable input in a function.
Type annotations allow you to specify the exact type of input and output you are passing around your functions. This not only leads to implicit assertions of your types, but also allows for great real-time syntax checking if you are using an editor that supports it.
Also, the next time you try and pass a boolean variable to a function expecting a string, your compiler will complain “LOUDLY” and refuse to compile your crap code. Using explicit variable types is the best documentation you can provide and its built into the code you are writing.

How to Install / Use It

Install TSC via NPM
npm install -g typescript
Then follow along in the easy to understand QuickStart / HelloWorld from the TS team: http://www.typescriptlang.org/docs/tutorial.html
If you cannot install it, you can also try the TS playground: http://www.typescriptlang.org/docs/tutorial.html

Who is really using TypeScript?

Well, for one, Microsoft is using it on quite a few internal projects. The Angular 2 team actually wrote the majority of the new framework using TypeScript. Also, the popular project management tool Asana’s team made a rather well publicized switch to TypeScript recently.

Should I use TypeScript?

The simple answer is, sure. Why not. I would give it a shot and try and work it into your workflow and see how it goes. Thankfully it plays nice with vanilla JS as well.
Leave us a note in the comments if you actually use TypeScript, or have a good reason not to use TypeScript, in your work.