How to write this java program using javascript and Node?

Question

public class Principal {

private static int x = 0;
private static int y = 0;

public static void sum() {
    x = y + 1;
    y = x + 1;
}

public static void main(String[] args) {

    for (int i = 1; i <= 10; i++) {

        Thread a = new Thread() {
            public void run() {
                sum();
            }
        };
        a.start();

        Thread b = new Thread() {
            public void run() {
                sum();
            }
        };
        b.start();

        System.out.println(x);
    }
  }
}

How can I write this algorithm using Node and javascript? I just don’t have a clue how to do it! I was analyzing some shapes and I found the Web Worker but I couldn’t do anything. What should I do? I don’t know how to work Node threads, I tried using this example Node-threads-a-Gogo but it seems that it does not run in windows.

Answer 1

Javascript has no threads. However you can run asynchronous methods. Example below:

var x = 0;
var y = 0;

function sum() {
  x = y + 1;
  y = x + 1;
}

function main() {

  for (i = 1; i <= 10; i++) {
    var a = setTimeout(function run(){ sum() }, 0);
    var b = setTimeout(function run(){ sum() }, 0);
  }

  console.log(x);

  // Complementar: Valor de X depois de 1 segundo.
  setTimeout(function(){ console.log(x); }, 1000);

}

main();

The result will be:

0
39

This is because asynchronous methods are declared and prepared for execution - but Scheduler does not invoke them until after the first console.log(x);. The second console call is there to show the result after a second.

Javascript has some native methods that provide asynchronous mechanisms. Among them:

• setInterval
• setTimeout
• requestAnimationFrame
• Xmlhttprequest
• Websocket
• Worker