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Игорь Новоженин
Asked:2020-06-29 23:27:09 +0000 UTC2020-06-29 23:27:09 +0000 UTC

将小写字母改为大写字母，将大写字母改为小写字母

  • 772

我想使用循环

var letters = "This iS a TeSt sTring";
for (i = 0; i++; i < str.length) {
    if (letters[i] === letters[i].toLowerCase())
         ...
}

更加困难。请告诉我如何正确编写代码。

javascript

5 个回答

  1. Best Answer

    function flipCase(str) {
  var chars = str.toUpperCase().split("");
  for (var i = 0; i < chars.length; i++) {
    if (chars[i] == str[i])
      chars[i] = chars[i].toLowerCase();
  }
  return chars.join("");
}

var letters = "This iS a TeSt sTring Щф";
var result = flipCase(letters);
console.log(letters);
console.log(result);

    • 5

  2. 如果我们假设字母可以是任何字母（不仅是拉丁字母），那么有几个选项是可能的，例如：

    const letters = "This iS a TeSt sTring";
let inverseLetters = '';

function invertLetter(letter) {
  return letter === letter.toLowerCase() ?
    letter.toUpperCase() :
    letter.toLowerCase();
}

for (const letter of letters) { inverseLetters += invertLetter(letter); }
console.log(inverseLetters);

inverseLetters = [...letters].map(invertLetter).join('');
console.log(inverseLetters);

inverseLetters = letters.replace(/./gu, invertLetter);
console.log(inverseLetters);

    如果支持Unicode 属性转义，您可以这样做：

    const letters = "This iS a TeSt sTring";
let inverseLetters = '';

function invertLetter(letter) {
  if (/\p{Lu}/u.test(letter)) return letter.toLowerCase();
  if (/\p{Ll}/u.test(letter)) return letter.toUpperCase();
  return letter;
}

for (const letter of letters) { inverseLetters += invertLetter(letter); }
console.log(inverseLetters);

inverseLetters = [...letters].map(invertLetter).join('');
console.log(inverseLetters);

inverseLetters = letters.replace(/\p{L}/gu, invertLetter);
console.log(inverseLetters);

    • 4 

  3. console.log("This iS a TeSt sTring".replace(/./g, c => {
  var u = c.toUpperCase()
  return c === u ? c.toLowerCase() : u
}))

    • 4 

  4. var letters = "This iS a TeSt sTring"
console.log(
  letters.replace(/([A-Z])|([a-z])/g, (_, u, l) => (
    u ? u.toLowerCase() : l.toUpperCase()
  ))
)

    • 3 

  5. console.log('HhH'.split('').map(k => k === k.toUpperCase() ? k.toLowerCase() : k.toUpperCase()).join(''));

console.log('This iS a TeSt sTring'.split('').map(k => k === k.toUpperCase() ? k.toLowerCase() : k.toUpperCase()).join(''));

    • 2

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