atomicIncrement.js

const threads = require("worker_threads");

if (threads.isMainThread) {
    let sharedBuffer = new SharedArrayBuffer(4);
    let sharedArray = new Int32Array(sharedBuffer);
    let worker = new threads.Worker(__filename, { workerData: sharedArray });

    worker.on("online", () => {
        for(let i = 0; i < 10_000_000; i++) {
            Atomics.add(sharedArray, 0, 1);  // Threadsafe atomic increment
        }

        worker.on("message", (message) => {
            // When both threads are done, use a threadsafe function
            // to read the shared array and confirm that it has the
            // expected value of 20,000,000.
            console.log(Atomics.load(sharedArray, 0));
        });
    });
} else {
    let sharedArray = threads.workerData;
    for(let i = 0; i < 10_000_000; i++) {
        Atomics.add(sharedArray, 0, 1);      // Threadsafe atomic increment
    }
    threads.parentPort.postMessage("done");
}