Friday, July 13, 2018

Re: Arrays and JSNI in J2CL

On Friday, July 13, 2018 at 2:57:10 PM UTC+2, Kirill Prazdnikov wrote:
Hi, I've heard that mysterious J2CL does not support JSNI, good.

But how then the Float32Array is implemented ?
As far as I know, there is no JSIndexer-like (hello TeaVM) annotation in JsInterop ?

Currently everyone is using JSNI llike 

  public static native float getF(Float32Array data, int i) /*-{
      return data[i];


Don't worry, there's an alternative to JSNI. Its usage is meant to be much smaller and exceptional than JSNI though.

Basically, you declare a method 'native' and give it a known name using JsInterop (i.e. annotate it with @JsMethod), and then in a JS file you can implement it, in "standard Closure way" (the class has the same name in JS as in Java, so you assign a function to MyClass.prototype.getF).
That said, for this specific case, you'd probably better extend JsArrayLike<Double> from jsinterop-base (this is what elemental2.core.Float32Array does; knowing that java.lang.Double is interchangeable with double as a representation of JS Number type, without any overhead); or implement the method by casting to JsArrayLike<Double>:
public static float getF(Float32Array data, int i) {
return Js.asArrayLike(this).getAnyAt(i).asFloat();

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