How can I perform a str replace in JavaScript replacing text in JavaScript

Question

I want to use str replace or its similar alternative to replace some text in JavaScript   var text    this is some sample text that i want to replace   var new text   replace in javascript  want    dont want   text   document write  new text      should give   this is some sample text that i dont want to replace      If you are going to regex  what are the performance implications in   comparison to the built in replacement methods

User · Accepted Answer

Using regex for string replacement is significantly slower than using a string replace.
As demonstrated on JSPerf, you can have different levels of efficiency for creating a regex, but all of them are significantly slower than a simple string replace. The regex is slower because:

Fixed-string matches don't have backtracking, compilation steps, ranges, character classes, or a host of other features that slow down the regular expression engine. There are certainly ways to optimize regex matches, but I think it's unlikely to beat indexing into a string in the common case.

For a simple test run on the JS perf page, I've documented some of the results:

_x000D_

<script>_x000D_
// Setup_x000D_
  var startString = "xxxxxxxxxabcxxxxxxabcxx";_x000D_
  var endStringRegEx = undefined;_x000D_
  var endStringString = undefined;_x000D_
  var endStringRegExNewStr = undefined;_x000D_
  var endStringRegExNew = undefined;_x000D_
  var endStringStoredRegEx = undefined;      _x000D_
  var re = new RegExp("abc", "g");_x000D_
</script>_x000D_
_x000D_
<script>_x000D_
// Tests_x000D_
  endStringRegEx = startString.replace(/abc/g, "def") // Regex_x000D_
  endStringString = startString.replace("abc", "def", "g") // String_x000D_
  endStringRegExNewStr = startString.replace(new RegExp("abc", "g"), "def"); // New Regex String_x000D_
  endStringRegExNew = startString.replace(new RegExp(/abc/g), "def"); // New Regexp_x000D_
  endStringStoredRegEx = startString.replace(re, "def") // saved regex_x000D_
</script>

_x000D_

The results for Chrome 68 are as follows:

String replace:    9,936,093 operations/sec
Saved regex:       5,725,506 operations/sec
Regex:             5,529,504 operations/sec
New Regex String:  3,571,180 operations/sec
New Regex:         3,224,919 operations/sec

From the sake of completeness of this answer (borrowing from the comments), it's worth mentioning that .replace only replaces the first instance of the matched character. Its only possible to replace all instances with //g. The performance trade off and code elegance could be argued to be worse if replacing multiple instances name.replace(' ', '_').replace(' ', '_').replace(' ', '_'); or worse while (name.includes(' ')) { name = name.replace(' ', '_') }

User · Answer

More simply    city name city name replace    gi         Replaces all spaces with

User · Answer

If you don t want to use regex then you can use this function which will replace all in a string  Source Code   function ReplaceAll mystring  search word  replace with         while  mystring includes search word                 mystring   mystring replace search word  replace with              return mystring        How to use   var mystring   ReplaceAll  Test Test    Test    Hello

User · Answer

Added a method replace in javascript which will satisfy your requirement  Also found that you are writing a string  new text  in document write   which is supposed to refer to a variable new text    x000D   x000D  let replace in javascript   replaceble  replaceTo  text    gt    x000D    return text replace replaceble  replaceTo  x000D    x000D   x000D  var text    this is some sample text that i want to replace   x000D  var new text   replace in javascript  want    dont want   text   x000D  document write new text   x000D   x000D   x000D

User · Answer

In ECMAScript 2021  you can use replaceAll can be used  const str    quot string1 string1 string1 quot  const newStr   str replaceAll  quot string1 quot    quot string2 quot     console log newStr       quot string2 string2 string2 quot

User · Answer

hm   Did you check replace      Your code will look like this  var text    this is some sample text that i want to replace   var new text   text replace  want    dont want    document write new text

User · Answer

You should write something like that    var text    this is some sample text that i want to replace   var new text   text replace  want    dont want    document write new text

User · Answer

Use JS String prototype replace first argument should be Regex pattern or String and Second argument should be a String or function   str replace regexp substr  newSubStr function    Ex   var str    this is some sample text that i want to replace   var newstr   str replace  want i   dont t want    document write newstr       this is some sample text that i don t want to replace

User · Answer

In Javascript  replace function available to replace sub-string from given string with new one  Use   var text    this is some sample text that i want to replace   var new text   text replace  want    dont want    console log new text     You can even use regular expression with this function  For example  if want to replace all occurrences of   with     var text    123 123 123   var new text   text replace    g        console log new text     Here g modifier used to match globally all available matches

User · Answer

Method to replace substring in a sentence using React    const replace in javascript    oldSubStr  newSubStr  sentence    gt        let newStr           let i   0      sentence split      forEach obj   gt          if  obj toUpperCase       oldSubStr toUpperCase              newStr   i     0   newSubStr   newStr         newSubStr          i   i   1          else           newStr   i     0   obj   newStr         obj          i   i   1                      return newStr         RunMethodHere

User · Answer

function str replace  old   new   text       return   text     split  old  join  new        You do not need additional libraries

User · Answer

The code that others are giving you only replace one occurrence  while using regular expressions replaces them all  like  sorgit said   To replace all the  want  with  not want   us this code   var text    this is some sample text that i want to replace   var new text   text replace  want g   dont want    document write new text     The variable  new text  will result in being  this is some sample text that i dont want to replace    To get a quick guide to regular expressions  go here  http   www cheatography com davechild cheat-sheets regular-expressions  To learn more about str replace    go here  https   developer mozilla org en-US docs JavaScript Reference Global Objects String replace Good luck

User · Answer

If you really want a equivalent to PHP s str replace you can use Locutus  PHP s version of str replace support more option then what the JavaScript String prototype replace supports  For example tags     PHP  bodytag   str replace   body     black     lt body text   body   gt           JS with Locutus var  bodytag   str replace    body     black     lt body text   body   gt        or array s    PHP  vowels   array  a    e    i    o    u    A    E    I    O    U     onlyconsonants   str replace  vowels       Hello World of PHP          JS with Locutus var  vowels     a    e    i    o    u    A    E    I    O    U    var  onlyconsonants   str replace  vowels       Hello World of PHP      Also this doesn t use regex instead it uses for loops  If you not want to use regex but want simple string replace you can use something like this   based on Locutus      x000D   x000D  function str replace  search  replace  subject    x000D   x000D    var i   0 x000D    var j   0 x000D    var temp      x000D    var repl      x000D    var sl   0 x000D    var fl   0 x000D    var f      concat search  x000D    var r      concat replace  x000D    var s   subject x000D    s      concat s  x000D   x000D    for  i   0  sl   s length  i  lt  sl  i      x000D      if  s i            x000D        continue x000D        x000D      for  j   0  fl   f length  j  lt  fl  j      x000D        temp   s i       x000D        repl   r 0  x000D        s i     temp  split f j   join repl  x000D        if  typeof countObj      undefined     x000D          countObj value      temp split f j    length - 1  x000D          x000D        x000D      x000D    return s 0  x000D    x000D  var text    this is some sample text that i want to replace   x000D   x000D  var new text   str replace   want    dont want   text  x000D  document write new text  x000D   x000D   x000D    for more info see the source code https   github com kvz locutus blob master src php strings str replace js

User · Answer

You would use the replace method   text   text replace  old    new      The first argument is what you re looking for  obviously  It can also accept regular expressions   Just remember that it does not change the original string  It only returns the new value

User · Answer

var new text   text replace  want    dont want

User · Answer

JavaScript has replace   method of String object for replacing substrings  This method can have two arguments  The first argument can be a string or a regular expression pattern  regExp object  and the second argument can be a string or a function  An example of replace   method having both string arguments is shown below   var text    one  two  three  one  five  one   var new text   text replace  one    ten    console log new text     ten  two  three  one  five  one   Note that if the first argument is the string  only the first occurrence of the substring is replaced as in the example above  To replace all occurrences of the substring you need to provide a regular expression with a g  global  flag  If you do not provide the global flag  only the first occurrence of the substring will be replaced even if you provide the regular expression as the first argument  So let s replace all occurrences of one in the above example    var text    one  two  three  one  five  one   var new text   text replace  one g   ten    console log new text     ten  two  three  ten  five  ten   Note that you do not wrap the regular expression pattern in quotes which will make it a string not a regExp object  To do a case insensitive replacement you need to provide additional flag i which makes the pattern case-insensitive  In that case the above regular expression will be  one gi  Notice the i flag added here   If the second argument has a function and if there is a match the function is passed with three arguments  The arguments the function gets are the match  position of the match and the original text  You need to return what that match should be replaced with  For example   var text    one  two  three  one  five  one   var new text   text replace  one g  function match  pos  text   return  ten       console log new text    ten  two  three  ten  five  ten   You can have more control over the replacement text using a function as the second argument

User · Answer

All these methods don t modify original value  returns new strings   var city name    Some text with spaces     Replaces 1st space with    city name replace               Returns  Some text with spaces   Replaces all spaces with   using regex  If you need to use regex  then i recommend testing it with https   regex101 com   city name replace    gi           Returns  Some text with spaces    Replaces all spaces with   without regex  Functional way   city name split      join           Returns  Some text with spaces

User · Answer

There are already multiple answers using str replace    which is fair enough for this question  and regex but you can use combination of str split   and join   together which is faster than str replace   and regex   Below is working example    x000D   x000D  var text    this is some sample text that i want to replace   x000D   x000D  console log text split  want   join  dont want     x000D   x000D   x000D

User · Answer

In JavaScript  you call the replace method on the String object  e g   this is some sample text that i want to replace  replace  want    dont want    which will return the replaced string   var text    this is some sample text that i want to replace   var new text   text replace  want    dont want       new text now stores the replaced string  leaving the original untouched

User · Answer

You can use   text replace  old    new     And to change multiple values in one string at once  for example to change   to string v and   to string w   text replace      g function match   return  match        v  w

User · Answer

that function replaces only one occurrence   if you need to replace   multiple occurrences you should try this function    http   phpjs org functions str replace 527   Not necessarily  see the Hans Kesting answer   city name   city name replace    gi

User · Answer

You have the following options    Replace the first occurrence    x000D   x000D  var text    this is some sample text that i want to replace and this i WANT to replace as well    x000D  var new text   text replace  want    dont want    x000D     new text is  this is some sample text that i dont want to replace and this i WANT to replace as well  x000D  console log new text  x000D   x000D   x000D     Replace all occurrences - case sensitive    x000D   x000D  var text    this is some sample text that i want to replace and this i WANT to replace as well    x000D  var new text   text replace  want g   dont want    x000D     new text is  this is some sample text that i dont want to replace and this i WANT to replace as well x000D  console log new text  x000D   x000D   x000D     Replace all occurrences - case insensitive     x000D   x000D  var text    this is some sample text that i want to replace and this i WANT to replace as well    x000D  var new text   text replace  want gi   dont want    x000D     new text is  this is some sample text that i dont want to replace and this i dont want to replace as well x000D  console log new text  x000D   x000D   x000D    More info -  here

[javascript] How can I perform a str_replace in JavaScript, replacing text in JavaScript?

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