JavaScript replace last occurrence of text in a string

Question

See my code snippet below   var list     one    two    three    four    var str    one two  one three  one four  one   for   var i   0  i  lt  list length  i           if  str endsWith list i                   str   str replace list i    finish               I want to replace the last occurrence of the word one with the word finish in the string  what I have will not work because the replace method will only replace the first occurrence of it  Does anyone know how I can amend that snippet so that it only replaces the last instance of  one

User · Accepted Answer

Well  if the string really ends with the pattern  you could do this   str   str replace new RegExp list i           finish

User · Answer

Here s a method that only uses splitting and joining  It s a little more readable so thought it was worth sharing       String prototype replaceLast   function  what  replacement            var pcs   this split what           var lastPc   pcs pop            return pcs join what    replacement   lastPc

User · Answer

A simple answer without any regex would be   str   str substr 0  str lastIndexOf list i       finish

User · Answer

str    str        replace list i          finish

User · Answer

You can use String lastIndexOf to find the last occurrence of the word  and then String substring and concatenation to build the replacement string   n   str lastIndexOf list i    if  n  gt   0  amp  amp  n   list i  length  gt   str length        str   str substring 0  n     finish          or along those lines

User · Answer

Thought I d answer here since this came up first in my Google search and there s no answer  outside of Matt s creative answer     that generically replaces the last occurrence of a string of characters when the text to replace might not be at the end of the string   if   String prototype replaceLast        String prototype replaceLast   function find  replace            var index   this lastIndexOf find            if  index  gt   0                return this substring 0  index    replace   this substring index   find length                      return this toString              var str    one two  one three  one four  one       outputs  one two  one three  one four  finish console log str replaceLast  one    finish         outputs  one two  one three  one four  one console log str replaceLast

User · Answer

Simple solution would be to use substring method  Since string is ending with list element  we can use string length and calculate end index for substring without using lastIndexOf method  str   str substring 0  str length - list i  length     finish

User · Answer

If speed is important  use this          Replace last occurrence of a string with another string    x - the initial string    y - string to replace    z - string that will replace     function replaceLast x  y  z       var a   x split          var length   y length      if x lastIndexOf y     -1            for var i   x lastIndexOf y   i  lt  x lastIndexOf y    length  i                  if i    x lastIndexOf y                     a i    z                            else                   delete a i                                      return a join          It s faster than using RegExp

User · Answer

I would suggest using the replace-last npm package    x000D   x000D  var str    one two  one three  one four  one   x000D  var result   replaceLast str   one    finish    x000D  console log result   x000D   lt script src  https   unpkg com replace-last latest replaceLast js  gt  lt  script gt  x000D   x000D   x000D    This works for string and regex replacements

User · Answer

I know this is silly  but I m feeling creative this morning    one two  one three  one four  one   split         array    one    two     one    three     one    four     one    reverse      array    one    four     one    three     one    two     one    join         string   one four  one three  one two  one   replace  one    finish      string   finish four  one three  one two  one   split         array    finish    four     one    three     one    two     one    reverse      array    one    two     one    three     one    four     finish    join          final string   one two  one three  one four  finish    So really  all you d need to do is add this function to the String prototype   String prototype replaceLast   function  what  replacement        return this split      reverse   join      replace new RegExp what   replacement  split      reverse   join            Then run it like so  str   str replaceLast  one    finish     One limitation you should know is that  since the function is splitting by space  you probably can t find replace anything with a space   Actually  now that I think of it  you could get around the  space  problem by splitting with an empty token   String prototype reverse   function          return this split     reverse   join          String prototype replaceLast   function  what  replacement        return this reverse   replace new RegExp what reverse     replacement reverse    reverse        str   str replaceLast  one    finish

User · Answer

I did not like any of the answers above and came up with the below function isString variable         return typeof  variable       string       function replaceLastOccurenceInString input  find  replaceWith        if   isString input      isString find      isString replaceWith                returns input on invalid arguments         return input             const lastIndex   input lastIndexOf find       if  lastIndex  lt  0            return input             return input substr 0  lastIndex    replaceWith   input substr lastIndex   find length       Usage  const input    ten eleven twelve thirteen fourteen fifteen sixteen seventeen eighteen nineteen twenty   const find    teen   const replaceWith    teenhundred    const output   replaceLastOccurrenceInString input  find  replaceWith   console log output       output  ten eleven twelve thirteen fourteen fifteen sixteen seventeen eighteen nineteenhundred twenty   Hope that helps

User · Answer

Couldn t you just reverse the string and replace only the first occurrence of the reversed search pattern   I m thinking        var list     one    two    three    four    var str    one two  one three  one four  one   for   var i   0  i  lt  list length  i           if  str endsWith list i                   var reversedHaystack   str split     reverse   join               var reversedNeedle   list i  split     reverse   join                reversedHaystack   reversedHaystack replace reversedNeedle   hsinif             str   reversedHaystack split     reverse   join

User · Answer

Not as elegant as the regex answers above  but easier to follow for the not-as-savvy among us   function removeLastInstance badtext  str        var charpos   str lastIndexOf badtext       if  charpos lt 0  return str      ptone   str substring 0 charpos       pttwo   str substring charpos  badtext length        return  ptone pttwo       I realize this is likely slower and more wasteful than the regex examples  but I think it might be helpful as an illustration of how string manipulations can be done   It can also be condensed a bit  but again  I wanted each step to be clear

User · Answer

Old fashioned and big code but efficient as possible   function replaceLast origin text       textLenght   text length      originLen   origin length     if textLenght    0          return origin       start   originLen-textLenght      if start  lt  0           return origin            if start    0           return               for i   start  i  gt   0  i--           k   0          while origin i k     text k                k               if k    textLenght                  break                    if k    textLenght              break              not founded     if k    textLenght          return origin         founded and i starts on correct and i k is the first char after     end   origin substring i k originLen       if i    0          return end      else          start   origin substring 0 i           return  start   end

[javascript] JavaScript: replace last occurrence of text in a string

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