FreeCodeCamp Bonfire - Search and Replace

search_and_replace.js

function replace(str, before, after) {
  // make sure before and after are the same case
  after = duplicateCase(before, after);

  // use RegExp object with global setting on
  var searchFor = new RegExp(before, 'g');

  return str.replace(searchFor, after);
}

function duplicateCase(sourceWord, modifiableWord) {
  // figure out the case of both words
  var sourceCase = isUpperCase(sourceWord);
  var modifiableCase = isUpperCase(modifiableWord);

  // if they are the same case, then return the second argument
  if (sourceCase === modifiableCase) {
    return modifiableWord;
  }
  else if (sourceCase && !modifiableCase) {
    // source is uppercase, modifiable is lower case
    return upperCaseWord(modifiableWord);
  }
  else {
    // source must be lower case and modifiable upper case
    return lowerCaseWord(modifiableWord);
  }
}

function isUpperCase(word) {
  // return True if the first letter of the argument is upperCase
  // false otherwise
  if (word.charCodeAt(0) >= 65 && word.charCodeAt(0) <= 90) {
    return true;
  }
  else {
    return false;
  }
}

function upperCaseWord(word) {
  var upperCaseLetter = word[0].toUpperCase();
  return upperCaseLetter + word.slice(1);
}

function lowerCaseWord(word) {
  var lowerCaseLetter = word[0].toLowerCase();
  return lowerCaseLetter + word.slice(1);
}