Replace last occurrence of character in string

Question

Is there an easy way in javascript to replace the last occurrence of an '_' (underscore) in a given string?

Is it always the last character of the string? If not, have a look at string.lastIndexOf(searchstring, start) — skarmats
– skarmats, Commented Mar 31, 2011 at 8:56
possible duplicate of How to replace last occurrence of characters in a string using javascript — Anderson Green
– Anderson Green, Commented Sep 4, 2014 at 5:41

Ry- · Accepted Answer · 2024-02-10 01:09:43Z

169

You can use a regular expression.

This will remove the last underscore:

var str = 'a_b_c';
console.log(  str.replace(/_([^_]*)$/, '$1')  ) //a_bc

This will replace it with the contents of the variable replacement:

var str = 'a_b_c',
    replacement = '!';

console.log(  str.replace(/_([^_]*)$/, replacement + '$1')  ) //a_b!c

edited Feb 10, 2024 at 1:09

Ry-♦

226k56 gold badges496 silver badges504 bronze badges

answered Mar 31, 2011 at 8:55

Martin Jespersen

26.3k8 gold badges60 silver badges69 bronze badges

Sign up to request clarification or add additional context in comments.

9 Comments

Pierpaolo Over a year ago

@Martin Jespersen: what if the text to be replaced is not the underscore but the content of a variable called replaceMe? How should the regex be modified?

Martin Jespersen Over a year ago

@Pierpaolo: You'd have to create the regexp using a new RegExp, read all about it here: developer.mozilla.org/en-US/docs/JavaScript/Guide/… - Remember to escape the replaceMe variable so it doesn't contain special characters that will alter the regular expression

Pierpaolo Over a year ago

@Martin Jespersen: thanks for the link. I already knew about the new RegExp syntax. My question was more like "where should I put the variable replaceMe"? e.g.: var aRegExpr = new RegExp("_([^"+replaceMe+"]*)$");

Martin Jespersen Over a year ago

@Pierpaolo: its not that simple tbh since you can have a word and not just a single char in a variable - you should start a new question about it :) It is too complicated for a comment here

Pierpaolo Over a year ago

Thanks. I understand, I will search whether there is already one.

|

mplungjan · Accepted Answer · 2019-06-10 14:42:04Z

79

No need for jQuery nor regex assuming the character you want to replace exists in the string

Replace last char in a string

str = str.substring(0,str.length-2)+otherchar

Replace last underscore in a string

var pos = str.lastIndexOf('_');
str = str.substring(0,pos) + otherchar + str.substring(pos+1)

or use one of the regular expressions from the other answers

var str1 = "Replace the full stop with a questionmark."
var str2 = "Replace last _ with another char other than the underscore _ near the end"

// Replace last char in a string

console.log(
  str1.substring(0,str1.length-2)+"?"
)  
// alternative syntax
console.log(
  str1.slice(0,-1)+"?"
)

// Replace last underscore in a string 

var pos = str2.lastIndexOf('_'), otherchar = "|";
console.log(
  str2.substring(0,pos) + otherchar + str2.substring(pos+1)
)
// alternative syntax

console.log(
  str2.slice(0,pos) + otherchar + str2.slice(pos+1)
)

edited Jun 10, 2019 at 14:42

answered Mar 31, 2011 at 8:52

mplungjan

180k29 gold badges183 silver badges246 bronze badges

5 Comments

jave.web Over a year ago

+1 for no regex & lastIndexOf(...) does the search from the END (better performance) so the currently accepted regexp even can't be faster.

tedebus Over a year ago

"nor regex".... this solution doesn't work if string doesn't contain the underscore. Regex version does. You can't add the substitution character if not needed.

mplungjan Over a year ago

@tedebus please read the question. Also some of the examples can handle any last character

tedebus Over a year ago

@mplungjan I read the question. In fact, my objection is related to the term "occurrence": there may be the element to be eliminated, but also not. The solution I read here adds a character regardless of whether it is necessary or not. I was not referring to the fact that the character could be different.

mplungjan Over a year ago

Updated to include that the char needs to exist

Harry Stevens · Accepted Answer · 2017-01-27 17:40:05Z

14

What about this?

function replaceLast(x, y, z){
  var a = x.split("");
  a[x.lastIndexOf(y)] = z;
  return a.join("");
}

replaceLast("Hello world!", "l", "x"); // Hello worxd!

answered Jan 27, 2017 at 17:40

Harry Stevens

1,4331 gold badge18 silver badges18 bronze badges

Comments

tensai · Accepted Answer · 2019-02-21 09:30:33Z

8

Another super clear way of doing this could be as follows:

let modifiedString = originalString
   .split('').reverse().join('')
   .replace('_', '')
   .split('').reverse().join('')

answered Feb 21, 2019 at 9:30

tensai

1,6963 gold badges18 silver badges23 bronze badges

Comments

vsync · Accepted Answer · 2019-11-21 15:19:29Z

5

var someString = "(/n{})+++(/n{})---(/n{})$$$";
var toRemove = "(/n{})"; // should find & remove last occurrence 

function removeLast(s, r){
  s = s.split(r)
  return s.slice(0,-1).join(r) + s.pop()
}

console.log(
  removeLast(someString, toRemove)
)

Breakdown:

s = s.split(toRemove)         // ["", "+++", "---", "$$$"]

s.slice(0,-1)                 //  ["", "+++", "---"]

s.slice(0,-1).join(toRemove)  // "})()+++})()---"

s.pop()                       //  "$$$"

edited Nov 21, 2019 at 15:19

answered Nov 21, 2019 at 15:08

vsync

133k61 gold badges345 silver badges430 bronze badges

Comments

Community · Accepted Answer · 2017-05-23 12:34:38Z

2

Reverse the string, replace the char, reverse the string.

Here is a post for reversing a string in javascript: How do you reverse a string in place in JavaScript?

edited May 23, 2017 at 12:34

CommunityBot

11 silver badge

answered Feb 19, 2013 at 22:36

sanon

6,5012 gold badges23 silver badges26 bronze badges

Comments

Steffan · Accepted Answer · 2018-05-04 19:28:33Z

2

    // Define variables
    let haystack = 'I do not want to replace this, but this'
    let needle = 'this'
    let replacement = 'hey it works :)'
    
    // Reverse it
    haystack = Array.from(haystack).reverse().join('')
    needle = Array.from(needle).reverse().join('')
    replacement = Array.from(replacement).reverse().join('')
    
    // Make the replacement
    haystack = haystack.replace(needle, replacement)
    
    // Reverse it back
    let results = Array.from(haystack).reverse().join('')
    console.log(results)
    // 'I do not want to replace this, but hey it works :)'

answered May 4, 2018 at 19:28

Steffan

7411 gold badge11 silver badges26 bronze badges

Comments

Partial Science · Accepted Answer · 2017-02-17 04:02:38Z

1

This is very similar to mplungjan's answer, but can be a bit easier (especially if you need to do other string manipulation right after and want to keep it as an array) Anyway, I just thought I'd put it out there in case someone prefers it.

var str = 'a_b_c';
str = str.split(''); //['a','_','b','_','c']
str.splice(str.lastIndexOf('_'),1,'-'); //['a','_','b','-','c']
str = str.join(''); //'a_b-c'

The '_' can be swapped out with the char you want to replace

And the '-' can be replaced with the char or string you want to replace it with

answered Feb 17, 2017 at 4:02

Partial Science

3282 silver badges6 bronze badges

Comments

mplungjan · Accepted Answer · 2019-06-11 06:56:03Z

-2

This is a recursive way that removes multiple occurrences of "endchar":

function TrimEnd(str, endchar) {
  while (str.endsWith(endchar) && str !== "" && endchar !== "") {
    str = str.slice(0, -1);
  }
  return str;
}

var res = TrimEnd("Look at me. I'm a string without dots at the end...", ".");
console.log(res)

edited Jun 11, 2019 at 6:56

mplungjan

180k29 gold badges183 silver badges246 bronze badges

answered Jun 10, 2019 at 13:59

tedebus

1,06015 silver badges23 bronze badges

Collectives™ on Stack Overflow

Replace last occurrence of character in string

9 Answers 9

9 Comments

5 Comments

Comments

Comments

Breakdown:

Comments

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

9 Answers 9

9 Comments

5 Comments

Comments

Comments

Breakdown:

Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related