JavaScript 2.0-The Complete Reference, Second ... - freecodingtutorial

Table 8-2: Regular Expression Escape Codes
Code Matches
>\uHHHH
Unicode
character
represented
by the
hexadecimal
value HHHH
>\cX
Control
character
represented
by ^X, for
example,
\cH
represents
CTRL-H
Unicode character represented by the hexadecimal value HHHH
Control character represented by ^X, for example, \cH represents CTRL-H
Using the appropriate escape code, we can now define a regular expression that matches
―http://www.w3c.org/‖ (and any other string containing it):
var pattern = /http:\/\/www\.w3c\.org\//;
Because / has special meaning in regular expression literals (it means the beginning or end of
the pattern), all the forward slashes (/) in the pattern are replaced with their escaped equivalent,
\/.
The important thing to remember is that whenever you want to include a character in a pattern
that has a special regexp meaning, you must use its escape code instead.
Repetition Quantifiers
Regular expression repetition quantifiers allow you to specify the number of times a particular
item in the expression can or must be repeated. For now, consider that by ―particular item‖ we
mean ―previous character.‖ The distinction will become clear later in the chapter. As an
example of a repetition quantifier, * (the asterisk) indicates that the previous item may occur
zero or more times. Any sequence of zero or more repetitions of the previous item can be
present in the strings the pattern will match. For example:
var pattern = /ab*c/;
Read the * as ―repeated zero or more times.‖ Doing so, we read this pattern as matching any
string containing an ―a‖ that is followed immediately by ―b‖ repeated zero or more times,
followed immediately by a ―c.‖ All the following strings will match this expression:
ac
abc
abbbbbbbbbbbbbbbbbbbbbbbbbbbc
The letters abc begin the alphabet
Similarly, + specifies that the previous character must be repeated one or more times. The
following declaration