Intermediate Algorithm Scripting - Search and Replace

Tell us what’s happening:
Describe your issue in detail here.

Your code so far

function myReplace(str, before, after) {
  let newStr = str.split(" ");
  let indexToReplace = newStr.indexOf(before);
  let firstLetter = "";

  if (before.charAt(0) === before.charAt(0).toUpperCase()) {
    firstLetter = after.charAt(0).toUpperCase();
    after = after.replace(after.charAt(0), firstLetter);
  } else {
    firstLetter = after.charAt(0).toLowerCase();
    after = after.replace(after.charAt(0), firstLetter);

  newStr.splice(indexToReplace, 1, after);

  return newStr.join(" ");

console.log(myReplace("I think we should look up there", "up", "Down"));
console.log(myReplace("He is Sleeping on the couch", "Sleeping", "sitting"));

**Your browser information:**

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**Challenge:**  Intermediate Algorithm Scripting - Search and Replace

**Link to the challenge:**

Welcome to the forum!
Your code passes the tests on my end. What issues do you have with this code?