Project Euler: Problem 5 - Smallest multiple | JavaScript

Question

This is my soloution for Project Euler: Problem 5 - Smallest multiple. Tell me if there is any way this could be improved:

main:
    for (var i = 1; true; i++) {
        for (var j = 1; j < 20; j++) {
            if (i % (j + 1) != 0) {
                continue main;
            }
        }
        document.write("Answer: " + i);
        break;
    }

Answer 1

Remarks

Your code solves this problem using very naive brute-force approach, which has polynomial complexity, i.e. \$O(n^c)\$. It's also pretty legacy and unusual, at least. Specifically, I'm talking i.a. about your use of label and document.write(). Moreover, it's a good habit to use identity operator wherever applicable.

Rewrite

Project Euler is a set of math-oriented programming challenges, and as such, authors of your problem sought for a solution that would use the least common multiple. Such solution has only linear complexity, i.e. \$O(n)\$, and it may be implemented in ES2015 (formerly ES6) as follows:

const lcm = n => {
  const gcd = (a, b) => b === 0 ? a : gcd(b, a % b);
  let result = 1;

  for (let i = 2; i <= n; i++) {
    result *= i / gcd(i, result);
  }
  return result;
};

console.log(lcm(20));

.as-console-wrapper { top: 0; }

Benchmark

Comparison of actual run times for various values of \$n\$ with regression curves and their \$R^2\$ (y-axis is in milliseconds per 30,000 runs).

Linear solution:

Your solution:

In this case, I run benchmark only for \$n<=8\$, because further ones took too long for my machine and patience.