[Interest] Changes to Javascript runtime in 5.12

Ulf Hermann ulf.hermann at qt.io
Thu Jan 3 10:22:15 CET 2019

Hi René,

> In JS libs before 5.12, I've always used a closure approach to not
> leak a bunch of private variables onto the global module object. This
> results in a layout much like so:
> (function(lib) {
>   ... closed vars can be declared here ...
>   lib.bar = function() {
>     return "baz";
>   };
> })(this);

You can still pass an empty object to your anonymous function and 
extract the interesting bits of that into the JS file's global scope 
afterwards. Or you can declare a number of vars outside the anonymous 
function and assign functions to them from inside. Both options are 
indeed a bit uglier, though.

This looks like a regression in Qt 5.12, but I will need to take a 
closer look at it. Did we ever document anything about the semantics of 
the "this" object in JavaScript libraries?

best regards,

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