CODEWITHSUNDEEP
javascriptjquery
bryan
bryan

Reputation: 9399

Replacing text only at end of string

So I have a few names such as: page_1.something.signature

I want to replace .signature with .date so I use something like:

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

But what if my string is page_1.signature.signature? Then my string ends up being page_1.date.signature.

So my question is, how do I only apply the replace function to the end of the string and ignore the .something?

Upvotes: 0

Views: 153

Answers (2)

David Thomas
David Thomas

Reputation: 253416

While you've already accepted an answer, I thought I'd offer a more functional approach to achieve a similar result, this approach replaces the last occurrence of the string passed to the function (whether it's at the end of the string, or otherwise). That said, here's the function:

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'

To demonstrate the output of several strings:

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>

References:

Upvotes: 0

garryp
garryp

Reputation: 5776

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

This approach uses a regular expression. The $ at the end means the string must end with the pattern before it. If you've not used regular expressions before , they're worth reading a about and make things like this easy.

Upvotes: 3

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