prime_eratosthene.js

const fs = require('fs');

const eratosthenes = (n) => {
    // Eratosthenes algorithm to find all primes under n
    let array = []
    let output = [];
    let upperLimit = Math.sqrt(n)

    // Make an array from 2 to (n - 1)
    for (var i = 0; i < n; i++) {
        array.push(true);
    }

    // Remove multiples of primes starting from 2, 3, 5,...
    for (var i = 2; i <= upperLimit; i++) {
        if (array[i]) {
            for (var j = i * i; j < n; j += i) {
                array[j] = false;
            }
        }
    }

    // All array[i] set to true are primes
    sum = 0;
    for (var i = 2; i < n; i++) {
        if(array[i]) {
            sum += i;
        }
    }

    return sum;
};

console.time('main')
let result = eratosthenes(1000000);
console.timeEnd('main')
console.log(result)

// fs.appendFileSync('data.txt', result + '\n', 'utf8')
// console.log(result)