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Clone this repository git clone https://github.com/graalvm/graal-js-jdk11-maven-demo
Move to the newly cloned directory cd graal-js-jdk11-maven-demo
Make sure that JAVA_HOME points at a JDK11 export JAVA_HOME=/path/to/jdk11
Open VSCode with VSNetBeans installed.
1. Go to File | Preferences and search for netbeans.jdkhome and set it to /path/to/jdk11
Open Folder with graal-js-jdk11-maven-demo in VSCode
Remove App.java and AppTest.java originally coming with the sample Maven project

Into main/java/com/mycompany/app add new File named PolyglotSample.java with following code:

Code Block

language	java
title	PolyglotSample.java
linenumbers	true
collapse	true

package  com.mycompany.app;
import org.graalvm.polyglot.Context;
import org.graalvm.polyglot.Source;
import org.graalvm.polyglot.Value;
import java.net.URL;

public class PolyglotSample {
    public static void main(String[] args) throws java.io.IOException, java.lang.InterruptedException {
        Context ctx = Context.create();
        URL fibUrl = PolyglotSample.class.getResource("fib.js");
        Source fibSrc = Source.newBuilder("js", fibUrl).build();
        Value fib = ctx.eval(fibSrc);
        for (int i = 0; i < 10; i++) {
            Value res = fib.execute(i);
            System.out.println("Polyglot with Graal.JS - fib(" + i + ") = " + res.asInt());
            Thread.sleep(500);
        }
    }
}

Then in terminal or file explorer create following structure where to store the JS source file so Java can find it, it has to be under main folder: resources/com/mycompany/app

Inside this resources/com/mycompany/app create file named fib.js and paste in following JS code:

Code Block

language	js
title	fib.js
linenumbers	true
collapse	true

(function(n) {
    function fib(x) {
        if (x <= 2) {
            return 1;
        }
        let fibX1 = fib(x - 1);
        let fibX2 = fib(x - 2);
        return fibX1 + fibX2;
    }
 
    let fibN = fib(n);
    print(`JavaScript computed that fib(${n}) is ${fibN}`);
 
    return fibN;
})

Save all files and invoke action from Command Palette: Java: Compile Workspace,
- this is the action provided by VSNetBeans which builds the project.
- Project is normally built also when debugger start but it is worth for the 1st time see if maven build passes.
After Once the build succeeds lets test the project.
Set breakpoint to line 11 in fib.js and
Select F5 to launch debugger and select type Java 8+ which is VSNetBeans provided debugger for JDK 8 and Polyglot capable of debugging Java and scripting languages like Graal.JS impl. of JS.
When started you should see something like following screenshot with Call Stack from JS to Java and variables from JS and Java depending on what context you have currently stepped into.

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