JavaScript Pocket Reference, 3rd Edition

Chapter 9. Regular Expressions

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. 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.

Describing Patterns with Regular Expressions

In JavaScript, regular expressions are represented by RegExp objects. RegExp objects may be created with the RegExp() constructor, of course, but they are more often created using a special literal syntax. Just as string literals are specified as characters within quotation marks, regular expression literals are specified as characters within a pair of slash (/) characters. Thus, your JavaScript code may contain lines like this:

var pattern = /s$/;

This line creates a new RegExp object and assigns it to the variable pattern. This particular RegExp object matches any string that ends with the letter “s.” This regular expression could have equivalently been defined with the RegExp() constructor like this:

var pattern = new RegExp("s$");

Regular-expression pattern specifications consist of a series of characters. Most characters, including all alphanumeric characters, simply describe characters to be matched literally. Thus, the regular expression ...