casefilter.js

function casefilter(input) {
  let inparray = input.split(""); // creates array of chars 
  let lower = ""; // string of lowercase characters
	let upper = ""; // string of uppercase characters
  for (let i = 0; i < inparray.length; i++) {
    let str = inparray[i].toString();
    let fixedstr = str.toUpperCase();
    if (str == " ") { // leave spaces separating words
      upper += str;
      lower += str;
    } else if (str == fixedstr) { // if char uppercase
      upper += str;
    } else {
      lower += str;
    }
  }
  return lower + "\n" + upper; // outputs the result to the console
}