Replace method of string object to search and replace part of a string in javascript

<script type="text/javascript">
var msg="Welcome to PHP tutorial section to learn PHP";
msg=msg.replace("PHP","JavaScript");
document.write(msg);
</script>

The output of the above code is

Welcome to JavaScript tutorial section to learn PHP

You can see we have successfully replaces the first occurrence of the word PHP ( search string here ) with JavaScript ( replace string). The second occurrence of the string PHP is not replaced.

So this way we can replace only one or the first find only. To replace all the matching search string we have to declared as global & use the regular expression syntax / in place of double quotes.

Here is the code to search and replace all occurrence string.

<script type="text/javascript">
var msg="Welcome to PHP tutorial section to learn PHP";
msg=msg.replace(/PHP/g,"JavaScript");
document.write(msg);
</script>

The output of above code will be

Welcome to JavaScript tutorial section to learn JavaScript

You must have observed this search and replace of string is case sensitive so if we replace search string by lower case text ( php ) then it will not able to match the string and replace with JavaScript. So we will modify the code little bit and add i to the command to make it case insensitive string replace.

msg=msg.replace(/php/gi,"JavaScript");

The full code is here.

<script type="text/javascript">
var msg="Welcome to PHP tutorial section to learn PHP";
msg=msg.replace(/php/gi,"JavaScript");
document.write(msg);
</script>

Now both the replacements have worked and the output is here

Welcome to JavaScript tutorial section to learn JavaScript

Syntax

str_var.replace("search_string", "replace_string")

JavaScript String Reference Searching string

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replace(): Search & replace of string

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