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JavaScript String - replace() Method

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Description

This method finds a match between a regular expression and a string, and replaces the matched substring with a new substring.

The replacement string can include the following special replacement patterns −

Pattern Inserts
$$ Inserts a "$".
$& Inserts the matched substring.
$` Inserts the portion of the string that precedes the matched substring.
$' Inserts the portion of the string that follows the matched substring.
$n or $nn Where n or nn are decimal digits, inserts the nth parenthesized submatch string, provided the first argument was a RegExp object.

Syntax

The syntax to use the replace() method is as follows −

string.replace(regexp/substr, newSubStr/function[, flags]);

Argument Details

  • regexp − A RegExp object. The match is replaced by the return value of parameter #2.

  • substr − A String that is to be replaced by newSubStr.

  • newSubStr − The String that replaces the substring received from parameter #1.

  • function − A function to be invoked to create the new substring.

  • flags − A String containing any combination of the RegExp flags: g - global match, i - ignore case, m - match over multiple lines. This parameter is only used if the first parameter is a string.

Return Value

It simply returns a new changed string.

Example

Try the following example.

Live Demo 
<html>
   <head>
      <title>JavaScript String replace() Method</title>
   </head>
   
   <body>   
      <script type = "text/javascript">
         var re = /apples/gi;
         var str = "Apples are round, and apples are juicy.";
         var newstr = str.replace(re, "oranges");        
         document.write(newstr ); 
      </script>      
   </body>
</html>

Output

oranges are round, and oranges are juicy.

Example

Try the following example; it shows how to switch words in a string.

Live Demo 
<html>
   <head>
      <title>JavaScript String replace() Method</title>
   </head>
   
   <body>     
      <script type = "text/javascript">
         var re = /(\w+)\s(\w+)/;
         var str = "zara ali";
         var newstr = str.replace(re, "$2, $1");
         document.write(newstr);
      </script>   
   </body>
</html>

Output

ali, zara
javascript_strings_object.htm
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