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

id, title, isRequired, challengeType, forumTopicId, localeTitle

id	title	isRequired	challengeType	forumTopicId	localeTitle
a0b5010f579e69b815e7c5d6	Search and Replace	true	5	16045	搜索和替换

Description

在这道题目中，我们需要写一个字符串的搜索与替换函数，它的返回值为完成替换后的新字符串。 这个函数接收的第一个参数为待替换的句子。 第二个参数为句中需要被替换的单词。 第三个参数为替换后的单词。 注意：
你需要保留被替换单词首字母的大小写格式。即如果传入的第二个参数为 "Book"，第三个参数为 "dog"，那么替换后的结果应为 "Dog" 如果你遇到了问题，请点击帮助。

Instructions

Tests

tests:
  - text: "<code>myReplace('Let us go to the store', 'store', 'mall')</code>应该返回 'Let us go to the mall'。"
    testString: assert.deepEqual(myReplace("Let us go to the store", "store", "mall"), "Let us go to the mall");
  - text: "<code>myReplace('He is Sleeping on the couch', 'Sleeping', 'sitting')</code>应该返回 'He is Sitting on the couch'。"
    testString: assert.deepEqual(myReplace("He is Sleeping on the couch", "Sleeping", "sitting"), "He is Sitting on the couch");
  - text: "<code>myReplace('This has a spellngi error', 'spellngi', 'spelling')</code>应该返回 'This has a spelling error'。"
    testString: assert.deepEqual(myReplace("This has a spellngi error", "spellngi", "spelling"), "This has a spelling error");
  - text: "<code>myReplace('His name is Tom', 'Tom', 'john')</code>应该返回 'His name is John'。"
    testString: assert.deepEqual(myReplace("His name is Tom", "Tom", "john"), "His name is John");
  - text: "<code>myReplace('Let us get back to more Coding', 'Coding', 'algorithms')</code>应该返回 'Let us get back to more Algorithms'。"
    testString: assert.deepEqual(myReplace("Let us get back to more Coding", "Coding", "algorithms"), "Let us get back to more Algorithms");

Challenge Seed

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

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

Solution

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);
}