How to Execute JavaScript Code and Functions in Java

JavaScript is a popular scripting language used for developing dynamic and interactive web pages. While JavaScript is primarily used in web development, it can also be used in other areas such as server-side scripting, desktop applications, and mobile apps. In this blog, we will explore how to execute JavaScript code and functions in Java.

To execute JavaScript code in Java, we can use the ScriptEngine class provided by the Java API. The ScriptEngine class is used to execute scripts written in various languages, including JavaScript. Here is a sample code that demonstrates how to execute JavaScript code in Java:

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

public class JavaScriptExecutor {
    public static void main(String[] args) {
        // Create a ScriptEngineManager object
        ScriptEngineManager manager = new ScriptEngineManager();

        // Get the JavaScript engine
        ScriptEngine engine = manager.getEngineByName("javascript");

        try {
            // Execute JavaScript code
            String script = "var a = 1 + 2; a;";
            Object result = engine.eval(script);

            // Print the result
            System.out.println(result);
        } catch (ScriptException e) {
            e.printStackTrace();
        }
    }
}

In this example, we create a ScriptEngineManager object and get the JavaScript engine using the getEngineByName method. Then we execute the JavaScript code using the eval method of the ScriptEngine class and store the result in an Object variable. Finally, we print the result to the console.

To execute JavaScript functions in Java, we can define the function in JavaScript code and then call it from our Java code using the ScriptEngine class. Here is a sample code that demonstrates how to execute JavaScript functions in Java:

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

public class JavaScriptFunctionExecutor {
    public static void main(String[] args) {
        // Create a ScriptEngineManager object
        ScriptEngineManager manager = new ScriptEngineManager();

        // Get the JavaScript engine
        ScriptEngine engine = manager.getEngineByName("javascript");

        try {
            // Define a JavaScript function
            String script = "function add(a, b) { return a + b; }";

            // Execute the JavaScript function and get the result
            engine.eval(script);
            Object result = engine.eval("add(1, 2)");

            // Print the result
            System.out.println(result);
        } catch (ScriptException e) {
            e.printStackTrace();
        }
    }
}

In this example, we define a JavaScript function called add that takes two arguments and returns their sum. Then we execute the function using the eval method of the ScriptEngine class and store the result in an Object variable. Finally, we print the result to the console.

In conclusion, the ScriptEngine class provided by the Java API allows us to execute JavaScript code and functions in Java. By leveraging the power of both languages, we can create more powerful and dynamic applications.