Question

所以我有一些名字，例如：page_1.something.signature

我想将.signature替换为.date，因此我使用类似的内容：

var string = "page_1.something.signature"
string = string.replace('.signature', '.date');

但是如果我的字符串是page_1.signature.signature怎么办？然后我的字符串最终成为page_1.date.signature。

所以我的问题是，我如何仅将替换函数应用于字符串的末尾并忽略 .something ？

Answer 1

var string = "page_1.something.signature"
string = string.replace(/\.signature$/, '.date');

此方法使用正则表达式。最后的$表示字符串必须以之前的模式结束。如果你之前没有使用正则表达式，那么就值得阅读一下，并且这样做很简单。

Answer 2

虽然你已经接受了答案，但我认为我会提供一种更实用的方法来实现类似的结果，这种方法取代最后一次出现的传递给函数的字符串（无论是它在字符串的末尾，或者其他）。也就是说，这是函数：

function replaceLastOccurrence(haystack, needle, replacement) {
  // if you don't supply the required arguments, or the string to
  // replace is not in the string we pass to the function) we do nothing
  // I chose to return haystack (if it exists) or false (if it does not):
  if (!haystack || !needle || !replacement || haystack.indexOf(needle) === -1) {
    return haystack || false;
  }


  // breaking original string into an array of single-characters:
  var newString = haystack.split('')

  // using Array.prototype.splice() to manipulate the array,
  // finding the sequence of characters beginning at the lastIndexOf()
  // the string you're looking to replace, removing the array-elements
  // equal to the length of the string you want to replace (needle.length)
  // and replacing those array elements with the replacement-string:
  newString.splice(haystack.lastIndexOf(needle), needle.length, replacement)

  // because splice manipulates the original array, but returns
  // the array-elements it removes, we here join the array back
  // together to form a String using Array.prototype.join(''):
  return newString.join('');
}

var string = 'page_1.something.signature.more.signature.keys',
    newString = replaceLastOccurrence(string, 'signature', 'date');

function replaceLastOccurrence(haystack, needle, replacement) {
  if (!haystack || !needle || !replacement || haystack.indexOf(needle) === -1) {
    return haystack || false;
  }
  var newString = haystack.split('')

  newString.splice(haystack.lastIndexOf(needle), needle.length, replacement)

  return newString.join('');
}

var string = 'page_1.something.signature.more.signature.keys',
  newString = replaceLastOccurrence(string, 'signature', 'date');

console.log(newString); // 'page_1.something.signature.more.date.keys'

演示几个字符串的输出：

function replaceLastOccurrence(haystack, needle, replacement) {
  if (!haystack || !needle || !replacement || haystack.indexOf(needle) === -1) {
    return haystack || false;
  }

  var newString = haystack.split('')

  newString.splice(haystack.lastIndexOf(needle), needle.length, replacement);
  return newString.join('');
}

var originals = document.querySelectorAll('.original');

Array.prototype.forEach.call(originals, function(original) {
  original.nextElementSibling.textContent = replaceLastOccurrence(original.textContent, 'signature', 'date');
});

ul,
li {
  list-style-type: none;
}
ul {
  margin-top: 4em;
}
li {
  border-bottom: 1px solid #ccc;
  padding: 0.2em 0.5em;
  margin: 0 0 0.5em 0;
}
.original::after {
  content: ': ';
}
.output {
  float: right;
}

<ul>
  <li><span class="original">something</span><span class="output"></span>
  </li>
  <li><span class="original">page_1.something.signature</span><span class="output"></span>
  </li>
  <li><span class="original">page_1.something.signature.another</span><span class="output"></span>
  </li>
  <li><span class="original">page_1.something.signature.signature</span><span class="output"></span>
  </li>
</ul>

参考文献：

仅在字符串末尾替换文本

2 个答案: