Kotlin JS doesn't add "new" keyword where needed

Question

I am creating interactive infographics using Google Charts and Kotlin JS. This is snippet from Quick Start Page.

var data = new google.visualization.DataTable();
<..>
var chart = new google.visualization.PieChart(document.getElementById('chart_div'));

Here "new" keyword is used. I tried to rewrite this code using Kotlin.

val data = google.visualization.DataTable();
<..>
val chart = google.visualization.PieChart(document.getElementById('chart_div'));

But an error occurred saying that "new" keyword is missing in lines above. So Kotlin to JS compiler haven't added the keyword where they should be. Here is compiled JavaScript code.

var data = google.visualization.DataTable();
<..>
var chart =  google.visualization.PieChart(document.getElementById('chart_div'));

Is there correct way to avoid the error without using js() function?

Thank you.

Could you also share the javascript code compiled from these kotlin lines? — Ilya
– Ilya, Commented Nov 10, 2019 at 3:55
If I'm reading this thread correctly, it looks like you need to use the js function for all native Javascript object creation anyway. Is your avoidance of js on principle, or did you see this type of call work without the js function elsewhere? — Jeff Bowman
– Jeff Bowman, Commented Nov 10, 2019 at 14:54
I would guess it's because a JavaScript function can be called with and without new, meaning very different things, and KT doesn't know which you mean. — Aluan Haddad
– Aluan Haddad, Commented Nov 10, 2019 at 15:14
@ЕгорПономарёв Yes, but that's a Kotlin class, not an arbitrary expression (google.visualization.DataTable); as far as Kotlin knows, maybe DataTable is a plain function. Perhaps you need corresponding external class headers as XMLHttpRequest does, but even then it's unclear whether it would work with the built-in google.visualization namespacing. — Jeff Bowman
– Jeff Bowman, Commented Nov 10, 2019 at 15:15

egorponomaryov · Accepted Answer · 2019-11-12 16:14:07Z

2

The reason why the new keyword was not added is because google variable hadn't been added with external keyword. With this one Kotlin generates correct code.

external object google {
    object visualization {
        class DataTable
    }
}

answered Nov 12, 2019 at 16:14

egorponomaryov

1851 silver badge9 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Kotlin JS doesn't add "new" keyword where needed

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related