Regular expression

Regular expression creation

Var re = /ab+c var re = /ab+c Var re = new RegExp("ab+c", "flags") var re = new RegExp("ab+c", "flags") / / through the string expression to create regular, need to escape character has the following several / / [] \ ^ $|? * + ()Copy the code

Method of expression

exec

Reg. Exec (STR)

/d(b+)d/g.exec(' CDBBDBSBZ ')Copy the code
match

Return [match data, capture data, index, input], usage: reg.match(STR)

/d(b+)d/g.match(' CDBBDBSBZ ')Copy the code
test

Return a Boolean value. Usage: reg.test(STR)

/d(b+)d/g.test(' CDBBDBSBZ 'Copy the code
matchAll TODO

Returns an iterator

search

Search (str.search) returns the matched index, -1 if not matched.

CDBBDBSBZ '. Search (/d(b+)d/gCopy the code
replace

Replace matching data, use: str.replace(reg, replace)

'CDBBDBSBZ '. Replace (/d(b+)d/g,' replace ') output: 'c replace BSBZ 'Copy the code
split

Split data according to specifications, usage: str.split(reg)

Split (/db+d/g) output: ['c', 'BSBZ ']Copy the code

List of special characters

Assertion class

  • ^: Matches the beginning of the input
  • $: Matches the end of the input
  • \b: Matches “word” and “non-word” boundaries
  • \B: Matches congener boundaries, that is, between “words” and “words”, and between “non-words” and “non-words”
  • x(? =y): Predicate forward, matchxbeyfollow
  • x(? ! y): Forward negate assertion, matchxDon’t beyfollow
  • (? <=y)x: Backward assertion, matchxfollowy
  • (? <! y)x: Backward negate assertion, matchxDon’t followy

[a-za-z0-9_], otherwise called “non-word”

Character classes

  • .: matches any single character except the terminator
  • \d: Matches any Arabic numeral. The equivalent of[0-9]
  • \D: match the\d. The equivalent of[^ 0-9]
  • \w: Matches alphanumeric characters in the basic Latin alphabet[A-Za-z0-9_]
  • \W: match the\w, which is equivalent to[^A-Za-z0-9_]
  • \s: Matches whitespace characters, including the following, equivalent to[\f\n\r\t\v\u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff]:
    • Space character
    • TAB character
    • Carriage Return character
    • New Line character
    • Vertical TAB character
    • Form Feed Character
  • \S: match the\s, which is equivalent to[^\f\n\r\t\v\u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff]
  • \tMatch:TAB character
  • \rMatch:Carriage Return character
  • \nMatch:New Line character
  • \vMatch:Vertical TAB character
  • \fMatch:Form Feed Character
  • [\b]Match:Backspace
  • \ 0: Matches NULL characters
  • \xhh: Matches two hexadecimal numbers
  • \uhhhh: Matches four hexadecimal and Unicode characters

Group and the scope of

  • x|yMatch:xorycharacter
  • [xyzA-Z]Match:AtoZThe character collection ofxyzThree characters in which-Is a hyphen and will be matched as a normal character if placed at the beginning or end
  • [^xyzA-Z]Matching except:[xyzA-Z]Characters other than
  • (x): Capture group, matchxAnd rememberx
  • \n: nIs a positive integer that references the previous capture, for example:/abc(d)ef\1/matchingabcdefg,abcdefd

quantifiers

  • x*Will:xMatch 0 times or more
  • x+Will:xMatch more than once
  • x?Will:xMatches 0 or 1 times
  • x{n}Will:xmatchingntime
  • x{n,}Will:xmatchingnMore than once
  • x{n,m}Will:xmatchingnMore than once,mTime in the following
  • x*? , x+? , x?? , x{n}? , x{n,}? , x{n,m}?: originallyx*, x+, x? , x{n}, x{n,}, x{n,m}The one that matches is greedy, plus?After that, the match becomes “non-greedy.”

PS: “greedy” means all matches, “non-greedy” means only one match

Regular expression flag

Regular expressions have six optional arguments (flags) to allow global and case-insensitive searches, etc. These parameters can be used alone or together in any order and are included in the regular expression instance

  • g: Global search
  • i: Case insensitive search
  • m: multi-line search
  • sThat would allow.Matches a newline character
  • u: Matches using patterns of Unicode codes
  • y: Performs the “sticky” search and matches the current position of the target string

reference

MDN- Regular expression