const workerCode = `
    function isPrime(num) {
        for (let i = 2; i < num / 2 + 1; i++)
            if (num % i === 0) return false;
        return num > 1;
    }

    function sumPrimes(start, end) {
        let sum = 0;

        for (let i = start; i <= end; i++)
            if (isPrime(i)) sum += i;

        return sum;
    }

    self.onmessage = function (e) {
        let startPrime = parseInt(e.data[0]);
        let endPrime = parseInt(e.data[1]);

        let sum = sumPrimes(startPrime, endPrime)

        postMessage(sum);

    };
`;

const workerBlob = new Blob([workerCode], {type: 'application/javascript'});

async function sumPrimes(num){

    return new Promise((resolve, reject) => {
        const THREAD_COUNT = navigator.hardwareConcurrency;

        let pice = Math.floor(num / THREAD_COUNT);
        let lastPice = pice + num % THREAD_COUNT;

        let sum = 0;

        let end = 0;

        let threadCompleted = 0;

        for(let i = 1; i <= THREAD_COUNT; i++){

            let p = i == THREAD_COUNT ? pice : lastPice;

            end += p;
            start = end - p + 1;

            //console.log(start, end);

            let worker = new Worker(URL.createObjectURL(workerBlob));
            worker.postMessage([start, end]);

            worker.onmessage = function(e) {
                sum += e.data;

                threadCompleted++;
                if(threadCompleted == THREAD_COUNT)
                    resolve(sum);

            }

        }

    });

}

(async () => {
    console.time('sumPrimes');
    let sum = await sumPrimes(300000);
    console.timeEnd('sumPrimes');

    console.log("Sum:", sum);
})();