@santi100/eratosthenes-sieve/src/index.ts

Santi's Energetic Sieve of Eratosthenes: How can you sift numbers?

import assertExclusiveMin = require('@santi100/assertion-lib/cjs/exclusive-min');
import assertTypeOf = require('@santi100/assertion-lib/cjs/type-of');
import assertInteger = require('@santi100/assertion-lib/cjs/integer');
import assertPositive = require('@santi100/assertion-lib/cjs/positive');

/**
 * Finds all prime numbers from 2 up to a given number `n`.
 * 
 * @param n The upper limit of the range of numbers to check for primes.
 */

function sieve(n: number): number[] {
    assertTypeOf(n, 'number', 'n');
    assertInteger(n, 'n');
    assertPositive(n, 'n');
    assertExclusiveMin(n, 1, 'n');

    if (n === 2) 
        return [n];

    const numbers: Record<number, boolean> = {};
    const limit = Math.floor(n ** 0.5);
    for (let i = 2; i <= n; i++) numbers[i] = false;
    for (let i = 2; i <= limit; i++) {
        if (!numbers[i]) {
            for (let j = i; j <= n / i; j++) {
                numbers[i * j] = true;
            }
        }
    }
    const results = [];
    for (const num in numbers) {
        if (!numbers[num]) results.push(Number(num));
    }
    return results;
}

export = sieve;