simple reg·u·lar ex·pres·sion

Attribute Character	Description
g	Global match. This looks for all matches of the pattern rather than stopping after the first match is found.
i	Pattern is case-insensitive. For example, McNeill and mcneill are considered the same pattern of characters.
m	Multi-line flag. Only available in IE 5.5+ and NN6+, this specifies that the special characters ^ and $ can match the beginning and the end of lines as well as the beginning and end of the string.

Special Characters

Attribute Character	Characters It Matches	Description
\d	Any digit from 0 to 9	\d\d matches 65, but not aa or 6a
\D	Any character that is not a digit	\D\D\D matches abc, but not 123 or 8ef
\w	Any word character; that is, A-Z, a-z, 0-9 and the underscore ( _ )	\w\w\w\w matches Ab_2, but not $%* or Ab_@
\W	Any non-word character	\w matches @, but not a
\s	Any whitespace character, including tab, newline, carriage return, formfeed and vertical tab	\s matches tab
\S	Any non-whitespace character	\S matches A, but not the tab character
.	Any single character other than the newline character ( \n )	. matches a or 4 or @
[...]	Any one of the characters between the brackets	[abc] will match a or b or c but nothing else [a-z] matches any character in the range a to z
[^...]	Any one character, but not one of those inside the brackets	[^abc] will match any character except a or b or c [^a-z] will match any character that is not in the range a to z

Repetition Characters

Special Character	Meaning	Example
{n}	Match n of the previous item.	x{2} matches xx
{n, }	Match n or more of previous item	x{2,} matches xx, xxx, xxxx, xxxxx and so on
{n,m}	Match at least n and at the most m of the previous item	x{2,4} matches xx, xxx and xxxx
?	Match the previous item zero or one time	x? matches x or nothing
+	Match the previous item one or more times	x+ matches x, xx, xxx, xxxx, xxxxx and so on
*	Match the previous item zero or more times	x* matches nothing, or x, xx, xxx, xxxx and so on

Position Characters

Position Character	Description
^	The pattern must be at the start of the string, or if it's a multi-line string, then at the beginning of a line. For multi-line text (a string that contains carriage returns), you need to set the multi-line flag when defining the regular expression string using /myregex/m. Note that this is only applicable to IE 5.5 and later and NN6 and later.
$	The pattern must be at the end of the string, or if it's a multi-line string, then at the end of a line. For multi-line text (a string that contains carriage returns), you need to set the multi-line flag when defining the regular expression string using /myregex/m. Note that this is only applicable to IE 5.5 and later and NN6 and later.
\b	This matches a word boundary, which is essentially the point between a word character and a non-word character.
\B	This matches a position that's not a word boundary.

The above content was assembled from:

Beginning JavaScript
by Paul Wilton, Jeremy McPeak
Paperback, Third Edition, 1032 pages
Published May 21st 2007 by Wrox (first published 2000)
ISBN 0470051515 (ISBN13: 9780470051511)