2. Regular expression character classes Character Matches
[...] Any one character between the brackets. [^...] Any one character not between the brackets. . Any character except newline or another Unicode line terminator. w Any ASCII word character. Equivalent to [a-zA-Z0-9_]. W Any character that is not an ASCII word character. Equivalent to [^a-zA-Z0-9_]. s Any Unicode whitespace character. S Any character that is not Unicode whitespace. Note that w and S are not the same thing. d Any ASCII digit. Equivalent to [0-9]. D Any character other than an ASCII digit. Equivalent to [^0-9]. [b] A literal backspace (special case). 3. Regular expression repetition characters Character Meaning {n,m} Match the previous item at least n times but no more than m times. {n,} Match the previous item n or more times. {n} Match exactly n occurrences of the previous item. ? Match zero or one occurrences of the previous item. That is, the previous item is optional. Equivalent to {0,1}. + Match one or more occurrences of the previous item. Equivalent to {1,}. * Match zero or more occurrences of the previous item. Equivalent to {0,}. 4。 Regular expression alternation, grouping, and reference characters Character Meaning | Alternation. Match either the subexpression to the left or the subexpression to the right. (...) Grouping. Group items into a single unit that can be used with *, +, ?, |, and so on. Also remember the characters that match this group for use with later references. (?:...) Grouping only. Group items into a single unit, but do not remember the characters that match this group. n Match the same characters that were matched when group number n was first matched. Groups are subexpressions within (possibly nested) parentheses. Group numbers are assigned by counting left parentheses from left to right. Groups formed with (?: are not numbered. 5. Regular-expression anchor characters Character Meaning ^ Match the beginning of the string and, in multiline searches, the beginning of a line. $ Match the end of the string and, in multiline searches, the end of a line. b Match a word boundary. That is, match the position between a w character and a W character or between a w character and the beginning or end of a string. (Note, however, that [b] matches backspace.) B Match a position that is not a word boundary. (?=p) A positive lookahead assertion. Require that the following characters match the pattern p, but do not include those characters in the match. (?!p) A negative lookahead assertion. Require that the following characters do not match the pattern p. 6. Regular-expression flags Character Meaning i Perform case-insensitive matching. g Perform a global matchthat is, find all matches rather than stopping after the first match. m Multiline mode. ^ matches beginning of line or beginning of string, and $ matches end of line or end of string.string.replace(regexp, replacement)
Characters Replacement $1, $2, ..., $99 The text that matched the 1st through 99th parenthesized subexpression within regexp $& The substring that matched regexp $' The text to the left of the matched substring $' The text to the right of the matched substring $$ A literal dollar sign name.replace(/(w+)s*,s*(w+)/, "$2 $1"); text.replace(/"([^"]*)"/g, "''$1''"); text.replace(/bw+b/g, function(word) { return word.substring(0,1).toUpperCase( ) + word.substring(1); });
