Why doesn't Game/App Lab support const/int variables?

JavaScript has variable declarations other that var, like const and int, but Game/App Lab doesn’t support those. Does anyone know why?

Great question!
Short answer: Game Lab & App Lab only support ES5 features for now. const and let, unfortunately, weren’t added until ES6.

Long answer: JavaScript does support other keywords for variable declaration as you mentioned. We use const and let all the time in our own code base. These are handy keywords that were added in ES6 (the 6th iteration of JavaScript) due to high demand. The tough part is that each new version of the JavaScript spec brings in lots of changes. Each browser has to update their interpreter to handle all these changes (in fact, Internet Explorer still lacks support for most ES6 features). Our own interpreter for Game Lab and App Lab, while a pretty fancy piece of software, was designed to work with the previous version of the JavaScript spec, ES5. It is a goal of ours to eventually be able to support all the new language features that are part of ES6, but it will be a lot of work to get there. So, in the meantime, we’re stuck with only var.

-Jessica, Code.org Engineer