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# Javascript String - replace() Method

## 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:

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

Here is the detail of parameters:

- 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:

Following example shows how to use the global and ignore case flags which permits replace to replace each occurrence of 'apples' in the string with 'oranges'.

    <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>

To understand it in better way you can Try it yourself.

## Example:

Following example shows how to switch words in a string:

    <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>

To understand it in better way you can Try it yourself.

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