This code demonstrate the use of Invocable interface to invoke a specific function of a script. The Invocable.invokeFunction() takes the function name with or without a parameter as the function’s parameter. The parameter value can be passed as a varargs.

package org.kodejava.script;

import javax.script.ScriptEngineManager;
import javax.script.ScriptEngine;
import javax.script.ScriptException;
import javax.script.Invocable;

public class InvokingFunction {
    public static void main(String[] args) {
        String script = """
                function sayHello() {
                   sayHello(null);
                }

                function sayHello(name) {
                   print('Hi there' + ((name == null) ? '!' : ' ' + name + '!'));
                }
                """;

        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByExtension("js");

        try {
            engine.eval(script);

            // Convert / cast the engine into invocable engine.
            Invocable invocableEngine = (Invocable) engine;

            // Invoking sayHello function without parameter.
            invocableEngine.invokeFunction("sayHello");

            // Invoking sayHello function with a parameter.
            invocableEngine.invokeFunction("sayHello", "Jude");
        } catch (ScriptException | NoSuchMethodException e) {
            e.printStackTrace();
        }
    }
}

This will output:

Hi there!
Hi there Jude!

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>org.graalvm.js</groupId>
        <artifactId>js</artifactId>
        <version>22.3.2</version>
    </dependency>
    <dependency>
        <groupId>org.graalvm.js</groupId>
        <artifactId>js-scriptengine</artifactId>
        <version>22.3.2</version>
    </dependency>
</dependencies>