Summary

Regular expressions are the tool JavaScript provides for matching and manipulating string data based on patterns. Regular expressions can be created using literal syntax or the RegExp() constructor and are used in String methods, such as match(), replace(), search(), and split(). Regular expression objects also provide test(), match(), and compile() methods for testing, matching, and replacing regexps. Regular expressions themselves are composed of strings of characters along with special escape codes, character classes, and repetition quantifiers. The special escape codes provide the means to include otherwise problematic characters, such as newlines and those characters that have a special meaning in regexps. Character classes provide a way to specify a class or range of characters that a string must or must not draw from. Repetition quantifiers allow you to specify the number of times a particular expression must be repeated in the string in order to match. Regular expressions are at times hard to get right, so they should be crafted with care. Properly used, they provide a very powerful way to recognize, replace, and extract patterns of characters from strings.