Regular expression tester.

About Widgex
Widgex is a JavaScript regular expression (regex) tester.
In the upper text box enter a regular expression pattern without surrounding slashes or flags (e.g. ^[a-zA-Z]+$). In the lower box enter the text within which you wish to search. Matches, if they exist, are displayed as you type. A popular source of ready-made patterns is RegExLib.com.
Daniel Davis

Basic Regex Reference

• \ Escape or unescape the following character.
  
• ^ Match the beginning of the text.
  
• $ Match the end of the text.
  
• * Find zero or more occurrences of the preceeding item.
  
• + Find one or more occurrences of the preceeding item.
  
• ? Find zero or one occurrence of the preceeding item.
  
• . (dot) Match any character except newline characters.
  
• | Match the preceeding or following item.
  

Visit W3Schools for a much more comprehensive guide to regular expressions and their usage in JavaScript.