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.