freeCodeCamp Intermediate Algorithm Scripting: Search and Replace

myReplace.js

// Perform a search and replace on the sentence using the arguments 
// provided and return the new sentence.

// First argument is the sentence to perform the search and replace on.

// Second argument is the word that you will be replacing (before).

// Third argument is what you will be replacing the second argument 
// with (after).

// Note
// Preserve the case of the first character in the original word when
// you are replacing it. For example if you mean to replace the word 
// "Book" with the word "dog", it should be replaced as "Dog"

function myReplace(str, before, after) {
  if (before.toLowerCase() !== before) {
    after=after.charAt(0).toUpperCase() + after.substring(1);
  }
  return str.replace(before, after);
}

myReplace("A quick brown fox jumped over the lazy dog", "jumped", "leaped");