JavaScript Pocket Reference

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JavaScript Pocket Reference

Anchoring match position

An anchor in a regular expression matches a position in a

string (such as the beginning or the end of the string) with-

out matching any of the characters of a string. It can be used

to restrict (or anchor) a match to a specific position within a

string.

Versions of JavaScript

Netscape has defined a number of versions of JavaScript.

Microsoft has released more-or-less compatible versions

under the name “JScript,” and the ECMA standards body

has released three versions of a JavaScript standard named

“ECMAScript”. The following paragraphs describe these var-

ious versions, and explain how they relate to each other.

Each entry in the reference section contains availability infor-

Character Meaning

a | b Match either a or b

(sub)

Group subexpression sub into a single term, and remember the text

that it matched

(?:sub) Group subexpression sub but do not number the group or

remember the text it matches (JS 1.5)

\n Match exactly the same characters that were matched by group

number

n

$n

In replacement strings, substitute the text that matched the nth

subexpression

Character Meaning

^, $ Require match at beginning/end of a string, or in multiline mode,

beginning/end of a line

\b, \B Require match at a word boundary/non-boundary

(?=p) Look-ahead assertion: require that the following characters match

the pattern p, but do not include them in the match. (JS 1.5)

(?! ...