GraalVM JavaScript Implementation

GraalVM provides an ECMAScript-compliant runtime to execute JavaScript and Node.js applications. It is fully standard compliant, execute applications with high performance, and provide all benefits from the GraalVM stack, including language interoperability and common tooling. This reference documentation provides information on available JavaScript engine configurations, the Node.js runtime, the javax.script.ScriptEngine implementation, multithreading support details, possible embedding scenarios, and more. To migrate the code previously targeted to the Nashorn or Rhino engines, migration guides are available.

Running JavaScript

GraalVM can run plain JavaScript code:

js [options] [filename...] -- [args]

Running Node.js

GraalVM is adapted to run unmodified Node.js applications. Applications can import npm modules, including native ones.

To run Node.js-based applications, use the node utility bundled with GraalVM by default:

node [options] [filename] [args]

To install a Node.js module, use the npm launcher from the GraalVM’s /bin folder. The npm command is equivalent to the default Node.js command and supports all Node.js APIs.

1. Install the colors and ansispan modules using npm install as follows:

npm install colors ansispan

After the modules are installed, you can use them from your application.

2. Add the following code snippet to a file named app.js and save it in the same directory where you installed the Node.js modules:

const http = require("http");
const span = require("ansispan");
require("colors");

http.createServer(function (request, response) {
    response.writeHead(200, {"Content-Type": "text/html"});
    response.end(span("Hello Graal.js!".green));
}).listen(8000, function() { console.log("Graal.js server running at http://127.0.0.1:8000/".red); });

setTimeout(function() { console.log("DONE!"); process.exit(); }, 2000);

3. Execute it on GraalVM using the node command as follows:

node app.js

For more information about running Node.js, continue to Node.js Runtime.

Interoperability

GraalVM supports several other programming languages like Ruby, R, Python, and LLVM languages. While GraalVM is designed to run Node.js and JavaScript applications, it also provides interoperability between those languages and lets you execute code from or call methods in any of those languages using GraalVM Polyglot APIs.

To enable Node.js or JavaScript interoperability with other languages, pass the --jvm and --polyglot options. For example:

node --jvm --polyglot
Welcome to Node.js v12.15.0.
Type ".help" for more information.
> var array = Polyglot.eval("python", "[1,2,42,4]")
> console.log(array[2]);
42
> console.log(Polyglot.eval('R', 'runif(100)')[0]);
0.8198353068437427

For more information about interoperability with other programming languages, see Polyglot Programming.

Interoperability with Java

To access Java from JavaScript, use Java.type, as in the following example:

node --jvm
> var BigInteger = Java.type('java.math.BigInteger');
> console.log(BigInteger.valueOf(2).pow(100).toString(16));
10000000000000000000000000

Vice versa, you can execute JavaScript from Java by embedding the JavaScript context in the Java program:

import org.graalvm.polyglot.*;
import org.graalvm.polyglot.proxy.*;

public class HelloPolyglot {

    static String JS_CODE = "(function myFun(param){console.log('hello '+param);})";

    public static void main(String[] args) {
        System.out.println("Hello Java!");
        try (Context context = Context.create()) {
            Value value = context.eval("js", JS_CODE);
            value.execute(args[0]);
        }
    }
}

By wrapping the function definition (()), you return the function immediately. The source code unit can be represented with a String, as in the example, a file, read from URL, and other means.

Run the above Java program:

javac HelloPolyglot.java
java HelloPolyglot JavaScript

This way you can evaluate JavaScript context embedded in Java, but you will not be able to call a function and set parameters in the function directly from the Java code. The Node.js runtime cannot be embedded into a JVM but has to be started as a separate process.

For example, save this code as app.js:

var HelloPolyglot = Java.type("HelloPolyglot");

HelloPolyglot.main(["from node.js"]);

console.log("done");

Then start node with the --jvm option to enable interoperability with Java:

node --jvm --vm.cp=. app.js
Hello Java!
hello from node.js
done

By setting the classpath, you instruct node to start a JVM properly. Both Node.js and JVM then run in the same process and the interoperability works using the same Value classes as above.

Learn more about language interoperability in the Java Interoperability guide.