I've tried that, but since data.canExchange is a bool, it will return true if "canExchange":false. That took me a looong while to circumvent. Any tips on how to make this cleaner is welcome ;)

@Nescio is right, it's better to specify in the resource.json if the resource is tradeable, barterable, and tributable. This way if you forget you will get a nice error like you did on the forums.

Then assume the value exists. Also can exchange is useless cause it's basically the combination of the three others.

this.resourceTradable[data.code] = data.canTrade;
if (data.canTrade == true)
{
    this.resourceTradables.push(data.code);
}

this.resourceBarterable[data.code] = data.canBarter;
if (data.canBarter == true)
{
    this.canBarter.push(data.code);
}

this.resourceTributable[data.code] = data.canTribute;
if (data.canTribute == true)
{
    this.resourceTributables.push(data.code);
}

I've tried that, but since data.canExchange is a bool, it will return true if "canExchange":false. That took me a looong while to circumvent. Any tips on how to make this cleaner is welcome ;)

Sounds like missing parenthesis https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence

if (typeof(data.canExchange) == "undefined" ? true : data.canExchange == true)
->
if (data.canExchange)
https://developer.mozilla.org/en-US/docs/Glossary/Falsy

If the property was not defined for some resources, then one can use if (!!data.canExchange) to circumvent the undefined warning.
But the property should also always be defined in the resource.

Well, I kind of got it working, is it okay like this?
I've done it like this because the resourceData cannot be sorted by the resSort.

Yep could definitely be made in a function.

It appeared that the = undefined was not necessary at all,,,

No, what this does is return empty if we pass a property that doesn't exist (see tests). If it wasn't there I think it would be a JS error.
Your code before handled this too I think, but it seemed less readable to me.

Ah, okay, then it is probably best to also alter the summary to reflect this ;)

Quite right :p
/me needs to read summaries more attentively.

I think it's saner to return nothing than everything, since that seems more ilike with what one would expect.

Agreed!

Yep I forgot it again ;)

I guess not? It is even worse: I use the other function nowhere.
But would this.GetTributable().filter(res => res).keys() return all resources in that object?

I still fail to grasp how the => thing works,,,

(res => res)

is equals to this

/**
 * @param {bool} a 
 */
let f = function (a)
{
    return a;
}

So in case of filter for each object of the array/object if the value is true, the object will be added in a new collection.

Then keys will only get the food, wood metal strings.

I still fail to grasp how the => thing works,,,

Arrow functions is just a different syntax for functions as Stan mentioned.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter

collection

(JS doesn't have collections afaik, only arrays and objects)

{ "food", "metal", ... }

That's not legal JS, braces indicate an object, but content indicates an array, so [ "val1", "val2", ...]

Is the performance so bad that you need to cache them instead of returning

When the resource-agnostic patch was done by s0600204 and me, we went for caching because there are only a handful of resources, so very few memory allocation and many references to resourceData, resourceDataObj, resourceCodes, resourceNames in GUI and simulation.

Here it's only GUI, and only upon trade/barter dialog resizing only, and upon player Commands. Still not a problem, and code consistency isn't so bad.
We also have to remember that globalscripts are loaded from scratch everytime a new GUI page is opened, each message box.

One must look at the actual callers to see if the caching makes any sense. (Actually doesn't look like it's really adding benefit, because the callers do tons of other stuff looping over resources already, but I can't go through these lines each now)

Here it's only GUI, (...)

Doesn't the AI call these functions also?