JavaScript Testing and Static Type Systems at Scale - @Scale 2014 - Web

Avik Chaudhuri, Software Engineer at Facebook and Jeff Morrison, Software Engineer at Facebook
To encourage engineers to continue to make changes to the codebase, we spent some time identifying various important traits around automated testing, and used our insights to build a tool (called Jest) that makes it as simple and straightforward as possible for developers to write tests. The code we write must not only exploit the full flexibility and expressiveness offered by the JavaScript language, but also clear an incredibly high bar for robustness, performance, and hackability. At Facebook, we're working on adding static types to JavaScript without disempowering the dynamism that makes JavaScript great.

[danielearwicker]

26:15 - perfect, 'union type' is the missing feature of TypeScript I was looking for :)

[burreld]

I feel like we are doing to much to make JavaScript support features that other languages use to make our code more reliable.

I feel Typescript and maybe future versions of JavaScript will become strongly type as a requirement.

The ease of learning in JavaScript and the skipping of steps to add functionality to an object make JavaScript a hard language to write reliable code. Every feature in JavaScript can be reproduced in standard OO languages like Java and C#. They sometime require more plumbing, but often force the dev to think though the problem.

I predict that JavaScript will evolve, just as C did(evolved to a fully OO language), to a fully function strongly typed language. To much money is being invested in various code bases around the world for this not to happen.

I also predict that JavaScript Ninjas around the world will resist this evolution. The proving ground will be in the cost of development and support. The longer we depend on JavaScript and the more options we have of evolved JavaScript or languages that cross compile to JavaScript, the sooner we will see the change.

The cost to maintain statically typed languages is far lower and allows for much larger code bases, than JavaScript alone.