freeCodeCamp/curriculum/challenges/chinese-traditional/02-javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/search-and-replace.md

id, title, challengeType, forumTopicId, dashedName

id	title	challengeType	forumTopicId	dashedName
a0b5010f579e69b815e7c5d6	搜索與替換	5	16045	search-and-replace

--description--

在這道題目中，我們需要寫一個字符串的搜索與替換函數，它的返回值爲完成替換後的新字符串。

這個函數接收的第一個參數爲待替換的句子。

第二個參數爲句中需要被替換的單詞。

第三個參數爲替換後的單詞。

注意： 在更換原始單詞時保留原始單詞中第一個字符的大小寫。 即如果傳入的第二個參數爲 Book，第三個參數爲 dog，那麼替換後的結果應爲 Dog

--hints--

myReplace("Let us go to the store", "store", "mall") 應返回 Let us go to the mall。

assert.deepEqual(
  myReplace('Let us go to the store', 'store', 'mall'),
  'Let us go to the mall'
);

myReplace("He is Sleeping on the couch", "Sleeping", "sitting") 應返回 He is Sitting on the couch。

assert.deepEqual(
  myReplace('He is Sleeping on the couch', 'Sleeping', 'sitting'),
  'He is Sitting on the couch'
);

myReplace("I think we should look up there", "up", "Down") 應返回 I think we should look down there。

assert.deepEqual(
  myReplace('I think we should look up there', 'up', 'Down'),
  'I think we should look down there'
);

myReplace("This has a spellngi error", "spellngi", "spelling") 應返回 This has a spelling error。

assert.deepEqual(
  myReplace('This has a spellngi error', 'spellngi', 'spelling'),
  'This has a spelling error'
);

myReplace("His name is Tom", "Tom", "john") 應返回 His name is John。

assert.deepEqual(
  myReplace('His name is Tom', 'Tom', 'john'),
  'His name is John'
);

myReplace("Let us get back to more Coding", "Coding", "algorithms") 應返回 Let us get back to more Algorithms。

assert.deepEqual(
  myReplace('Let us get back to more Coding', 'Coding', 'algorithms'),
  'Let us get back to more Algorithms'
);

--seed--

--seed-contents--

function myReplace(str, before, after) {
  return str;
}

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

--solutions--

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