A regular expression is an object that
describes a pattern of characters. The JavaScript RegExp class
represents regular expressions, and both String and RegExp define
methods that use regular expressions to perform powerful
pattern-matching and search-and-replace functions on text. JavaScript’s
regular expression grammar is a fairly complete subset of the
regular-expression syntax used by Perl 5, so if you are an experienced
Perl programmer, you already know how to describe patterns in
JavaScript.[17]
This chapter begins by defining the syntax that regular
expressions use to describe textual patterns. It then moves on to
describe the String and RegExp methods that use regular
expressions.
[17] Perl regular expression features that are not supported by
ECMAScript include the s
(single-line mode) and x
(extended syntax) flags; the \a
,
\e
, \l
, \u
,
\L
, \U
, \E
,
\Q
, \A
, \Z
,
\z
, and \G
escape sequences; the (?<=
positive
look-behind anchor and the (?<!
negative look-behind anchor; and
the (?#
comment and the other
extended (?
syntaxes.