JsInterop Array

[cesar paulo alves]

Hello guys, so I'm getting crazy with this.

I need to inject a java array inside a javascript library.

The problem is that the Js library will iterate over an integer array, and if the element is not an integer it exits the function.

When I create the integer array and pass it to plain javascript array, for some reason it carries garbage inside, I already tried everything with no success.

So this is my java nodeset (https://pastebin.com/AdJqj80p)

I'm using the gwt-interop-utils -> https://github.com/GWTReact/gwt-interop-utils/blob/master/src/gwt/interop/utils/client/plainobjects/JsPlainObj.java

And when I inspect the javascript object in the browser you can see it has lots of garbage, and I cant clean it. See the nodes array I have (_clazz_0_g$,__elementTypeCategory$,_elementTypeId$"......).

And when I do the same with Js I don't have this garbage (obvious).

I already used the JsArray and everything, but no luck =/.

Do you have any Idea how to have a plain javascript array with jsInterop?

Thanks a lot.

[Vassilis Virvilis]

I had a similar problem with DataTables requiring a String[] argument. The one generated from java had some hidden fields that DataTables choke on. I ended up creating a JsString type that casts from/to String, but at the time I didn't know or didn't exist the gwt-interop-utils.

In your case however I would suggest the following:

*** NOTE:  int and int[] are not represented in javascript *** and you may have a problem during casting in/out. I would suggest using double if/when you hit the problems. Traceback and browser's debugger is invaluable.

@JsType(isNative = true, namespace = JsPackage.GLOBAL, name = "Object")

public class NodeSet {
  public int id;
  public int x;   <-- conside use of double
  public int y;
  public int[] nodes;

  @JsOverlay
  public static NodeSet create(int id, int x, int y, int[] nodes) {
      final NodeSet ns = new NodeSet();
      ns.id = id;
      ns.x = x;
      ns.y = y;
      ns.nodes = nodes;
      return ns;
  }
}

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Vassilis Virvilis

[Thomas Broyer]

This is not "garbage", they are "expando properties".

It shouldn't be a problem in practice for any well-coded JS lib. If your JS lib fails here, it probably means it iterates over the array using a for…in loop: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...in#Array_iteration_and_for...in

As a workaround, you can probably copy the array into a JsArrayInteger:

JsArrayInteger arr = JavaScriptObject.createArray().cast();
for (int node : nodes) {
  arr.push(node);
}

or using Elemental2 Core:

JsArray<Double> arr = new JsArray<>();
for (int node : nodes) {
  arr.push(node)
}

[cesar paulo alves]

Ok guys, so I apologize, after a few tests I realized something, as Thomas said about the js lib should't be reading the content, I went digger and realized that the problem was not on the expando properties but the name of the nodeSet array... The js looked for a "nodeSet" array and I was passing it as "nodeSets" array. Very sad (I'm not good with javascript). Thanks for all your help Vassills and Thomas.

I switched my code as Vassils as suggested and could find the bug(me) because of what Thomas said. Thanks a lot and sorry for taking your time.

Merry Christmas to all of you.

Cheers,

César Alves

[Colin Alworth]

Beware using JsArray<Double>, instead use JsArray<JsNumber>, see https://github.com/google/elemental2/issues/28.

A third option, with elemental2-core, rather than explicitly copying the array, ask the browser to do it for you with slice(). First cast the array to JsArray<JsNumber>, then slice it to get a copy of its contents, without the expandos.

JsArray<JsNumber> nodesJsArray = Js.cast(nodes);
JsNumber[] noExtraProperties = nodesJsArray.slice();

This can be handy when passing the int[] to something which refuses to handle extraneous properties, like window.postMessage. Yes, it is confusing that it appears you actually end up with a Java array, but it will not have those extra properties in this case.