Trying to find factors of a number in JS

Question

I am just starting JS, and understand the concept of finding a factor. However, this snippet of code is what I have so far. I have the str variable that outputs nothing but the

Answer 1

I came looking for an algorithm for this for use in factoring quadratic equations, meaning I need to consider both positive and negative numbers and factors. The below function does that and returns a list of factor pairs. Fiddle.

function getFactors(n) {
  if (n === 0) {return "∞";} // Deal with 0
  if (n % 1 !== 0) {return "The input must be an integer.";} // Deal with non-integers

  // Check only up to the square root of the absolute value of n
  // All factors above that will pair with factors below that
  var absval_of_n = Math.abs(n),
      sqrt_of_n = Math.sqrt(absval_of_n),
      numbers_to_check = [];
  for (var i=1; i <= sqrt_of_n; i++) {
    numbers_to_check.push(i);
  }

  // Create an array of factor pairs
  var factors = [];
  for (var i=0; i <= numbers_to_check.length; i++) {
    if (absval_of_n % i === 0) {
      // Include both positive and negative factors
      if (n>0) {
        factors.push([i, absval_of_n/i]);
        factors.push([-i, -absval_of_n/i]);
      } else {
        factors.push([-i, absval_of_n/i]);
        factors.push([i, -absval_of_n/i]);
      }
    }
  }

  // Test for the console
  console.log("FACTORS OF "+n+":\n"+
              "There are "+factors.length+" factor pairs.");
  for (var i=0; i