VKen · November 25, 2019 17:02
diff --git a/lcm.js b/lcm.js
 /* get the lowest common multiple from a sequential range of numbers
 expect arr = [a, b], where `a` and `b` are the (inclusive) edge range of natural numbers
 */
 function smallestCommons(arr) {
  let min = Math.min(...arr), max = Math.max(...arr),
  numList = Array.from(Array(max - min +1).keys(), (val) => val + min),
  factorMap = {};
  
  numList.forEach((val) => {  // generate the prime factors count mapping
    for (let [key, value] of Object.entries(primeFactor(val))) {
      if (!factorMap.hasOwnProperty(key)) factorMap[key] = value;
      if (factorMap[key] < value) factorMap[key] = value;
    }
  })

  return [...Object.entries(factorMap)].map(
    (val) => { return Math.pow(parseInt(val[0]), val[1])}
  ).reduce((acc, val) => acc * val);
 }

 /* get the prime factors of any given natural number above 1, using Sieve of Eratosthenes */
 function primeFactor(num) {  // prime factorization
  let factors = [];

  // handle even prime number
  while (num % 2 === 0) {
    factors.push(2);
    num /= 2;
  }

  if (num >= 3) {  // starting from the smallest odd-number prime
    // handle the odd prime numbers
    Array.from(
      Array(Math.ceil(Math.sqrt(num)) - 3 + 1).keys(),
      (val) => val * 2 + 3
    ).forEach((val) => {
      while (num % val == 0) {
        factors.push(val);
        num /= val;
      }
    });
    
    // leftover number is prime
    if (num > 2) factors.push(num);
  }
  
  // create a prime factors mapping `{prime_number[1]: index[1], ...prime_number[n]: index[n]}`
  // where prime_num ^ index = factor of number
  let primeFactorMap = {};
  factors.forEach((val) => {
    if (!primeFactorMap.hasOwnProperty(val.toString())) {
      primeFactorMap[val.toString()] = 0
    }
    primeFactorMap[val.toString()] += 1;
  })

  return primeFactorMap;
 }

 console.log(smallestCommons([23, 18]));  // Output: 6056820
	/* get the lowest common multiple from a sequential range of numbers
	expect arr = [a, b], where `a` and `b` are the (inclusive) edge range of natural numbers
	*/
	function smallestCommons(arr) {
	let min = Math.min(...arr), max = Math.max(...arr),
	numList = Array.from(Array(max - min +1).keys(), (val) => val + min),
	factorMap = {};

	numList.forEach((val) => { // generate the prime factors count mapping
	for (let [key, value] of Object.entries(primeFactor(val))) {
	if (!factorMap.hasOwnProperty(key)) factorMap[key] = value;
	if (factorMap[key] < value) factorMap[key] = value;
	}
	})

	return [...Object.entries(factorMap)].map(
	(val) => { return Math.pow(parseInt(val[0]), val[1])}
	).reduce((acc, val) => acc * val);
	}

	/* get the prime factors of any given natural number above 1, using Sieve of Eratosthenes */
	function primeFactor(num) { // prime factorization
	let factors = [];

	// handle even prime number
	while (num % 2 === 0) {
	factors.push(2);
	num /= 2;
	}

	if (num >= 3) { // starting from the smallest odd-number prime
	// handle the odd prime numbers
	Array.from(
	Array(Math.ceil(Math.sqrt(num)) - 3 + 1).keys(),
	(val) => val * 2 + 3
	).forEach((val) => {
	while (num % val == 0) {
	factors.push(val);
	num /= val;
	}
	});

	// leftover number is prime
	if (num > 2) factors.push(num);
	}

	// create a prime factors mapping `{prime_number[1]: index[1], ...prime_number[n]: index[n]}`
	// where prime_num ^ index = factor of number
	let primeFactorMap = {};
	factors.forEach((val) => {
	if (!primeFactorMap.hasOwnProperty(val.toString())) {
	primeFactorMap[val.toString()] = 0
	}
	primeFactorMap[val.toString()] += 1;
	})

	return primeFactorMap;
	}

	console.log(smallestCommons([23, 18])); // Output: 6056820