javascript regular expression Description

To create a regular expression object, surround the pattern with forward slashes, and assign the whole expression to a variable. For example, the following statement creates a regular expression with a pattern that is a simple word:

var re = /greet/;

The re variable can then be used as a parameter in a variety of methods that search for the pattern within some string (you may also use an expression directly as a method parameter, rather than assigning it to a variable).

Regular expression notation also consists of a number of metacharacters that stand in for sometimes complex ideas, such as the boundary on either side of a word, any numeral, or one or more characters. For example, to search for the pattern of characters shown above but only when the pattern is a word (and not part of a word such as greetings), the regular expression notation uses the metacharacters to indicate that the pattern includes word boundaries on both sides of the pattern:

var re = /\bgreet\b/;

The following table shows a summary of the regular expression notation used in JavaScript 1.2.

When you create a regular expression, you may optionally wire the expression to work globally (as you probably do if the regular expression is doing a search-and-replace operation with a method, and your goal is a "replace all" result) and to ignore case in its matches. The modifiers that turn on these switches are the letters g and i. They may be used by themselves or together as gi.

Once you have established a pattern with the regular expression notation, all the action takes place in the regular expression object methods and the String object methods that accept regular expression parameters.