javascript - Difference between w and  regular expression meta characters

Question

Can anyone explain the difference between and w regular expression metacharacters? It is my understanding that both these metacharacters are used for word boundaries. Apart from this, which meta character is efficient for multilingual content?

Answer 1

The metacharacter is an anchor like the caret and the dollar sign. It matches at a position that is called a "word boundary". This match is zero-length.

There are three different positions that qualify as word boundaries:

• Before the first character in the string, if the first character is a word character.
• After the last character in the string, if the last character is a word character.
• Between two characters in the string, where one is a word character and the other is not a word character.

Simply put: allows you to perform a "whole words only" search using a regular expression in the form of word. A "word character" is a character that can be used to form words. All characters that are not "word characters" are "non-word characters".

In all flavors, the characters [a-zA-Z0-9_] are word characters. These are also matched by the short-hand character class w. Flavors showing "ascii" for word boundaries in the flavor comparison recognize only these as word characters.

w stands for "word character", usually [A-Za-z0-9_]. Notice the inclusion of the underscore and digits.

B is the negated version of . B matches at every position where does not. Effectively, B matches at any position between two word characters as well as at any position between two non-word characters.

W is short for [^w], the negated version of w.