Javascript Regular Expression Tester

This page is an online tester with full syntactical support for JavaScript (JS) Regular Expressions (REs) and Replacement Expressions.  It can be used to test REs too difficult, inconvenient, or inefficient to test within code under development.

All of the RE and String methods/functions which use REs can be tested  -  the input for specifying a replacement expression is only displayed when the appropriate method is selected.

You can specify the RE with or without bounding slashes (/), but when they're included, the checkboxes defining switches are ignored; any required switches must be included in the RE text.

Copy Output To Input can be used when testing a conversion process with several steps.

Notes:

1. You will need to double up backslashes (\) when pasting as string literals REs tested here into JS source code;
2. JS handling of REs varies from interpreter to interpreter, and therefore browser to browser  -  for example:
   • Particularly on replacement, treatment of end-of-line (EOL) characters may depend on browser, source of input text, and Operating System (OS)  -  to replace EOLs successfully you may have to specify \x0D\x0A rather than \n;
   • Some very complex REs can hang FF3.

Useful links (no endorsement of external sites intended nor responsibility taken for their content):

• Microsoft Developer Network - Regular Expression Syntax (Scripting)
• W3Schools - JavaScript RegExp Object Reference