In the code editor, while editing a QML file, you get colors and such for core javascript concepts.

For instance:

for (let x in myList) doSomething()

this gives useful colors, 'for' is a keyword, 'let' is a different color', the braces are a boring color. And indeed 'in' (as part of the for loop) is the same color as 'let'.

When you use the second special for loop in JavaScript you replace the 'in' with 'of'. Like this;

for (let x of myList) doSomething()

It would be consistent and nice if the 'of' in that line were to get a consistent color. In my version of Qt Creator it is just a boring gray. Just like the braces and the semicolons are. It looks like QtCreator doesn't recognize this form of loop at all for the color highlighting.