How to use / g / I / m in javascript regular expression tag
This article mainly introduces the javascript regular expression tag / g / I / m how to use, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let Xiaobian take you to understand.
First, the js regular logo / gmeme hash iGrample
1 globle Universe g indicates that the expression will be used to find all possible matches in the input string, full-text search for all matching characters that appear, and multiple results can be returned. If you don't add / g, there will only be one match at most.
2 ignorCase I (pencil) indicates that matching is case-insensitive
Ignore case, note that only case is ignored, not half-width.
3Give mutiple means multi-line matching. What is multi-line matching for multi-line search? Is the potential match at both ends of the newline character. Influence the ^ $symbol in the rule
M affects ^, $.
If you do not specify m, then: ^ is only at the beginning of the string and $is only at the end of the string. That is, match the beginning and end of the entire string
If you specify m, then: ^ is at the beginning of each line of the string and $is at the end of each line of the string. That is, match the beginning and end of each line
Second, examples are illustrated.
The usage of 1.
Str = "tankZHang (231144)" + "tank ying (155445)"; res = str.match (/ tank/); / / No / g alert (res) is added; / / display a tank res = str.match (/ tank/g); / / add / g alert (res); / / display as tank,tank
2. The usage of "Zhonqingi".
Str = "tankZHang (231144)" + "tank ying (155445)"; res = str.match (/ zhang/); alert (res); / / displayed as null res = str.match (/ zhang/i); / / added / I alert (res); / / displayed as ZHang
The usage of 3.
Var p = / $/ mg; var s ='1\ N2\ n3\ n4\ n5\ n6; alert (p.test (s)); / / display as true alert (RegExp.rightContext.replace (/\ x0A/g,'\\ a'); / / display\ a2\ a3\ a4\ a5\ a6 alert (RegExp.leftContext); / display as vertical 2345 alert (RegExp.rightContext); / / display as 6 var p = / $/ g Var s ='1\ N2\ n3\ n4\ n6; alert (p.test (s)); / / display as true alert (RegExp.rightContext.replace (/\ x0A/g,'\ a')); / / nothing shows alert (RegExp.leftContext); / / shows vertical 123456 alert (RegExp.rightContext); / / nothing shows var p = / ^ / mg; var s ='1\ N2\ n3\ N4\ N5\ N6' Alert (p.test (s)); / / display as true alert (RegExp.rightContext.replace (/\ x0A/g,'\\ a')); / / display as 1\ a2\ a3\ a4\ a5\ a6 alert (RegExp.leftContext); / / display as vertical 12345 alert (RegExp.rightContext); / / display as 6
/ / as can be seen from the above example, the division of ^ $affected by / m
The three examples mentioned above, respectively, can be used in arrangement and combination. Personally, I don't think / m is of much use.
Supplementary note:
\ nmatches a newline character. Equivalent to\ x0a and\ cJ
RightContext
RegExp.rightContext ($')
This feature is non-standard, please try not to use it in a production environment!
RightContext non-standard attributes are static and read-only attributes of regular expressions, with the most recently matched right substring. RegExp.$' is an alias for this property.
Grammar
RegExp.rightContext
RegExp ["$'"]
Description
The rightContext property is static, not a property of a regular expression independent object. Instead, you should always use it as RegExp.rightContext or RegExp ["$'].
The value of the rightContext property is read-only and is modified when the match succeeds.
You cannot use a property accessor (RegExp.$') to use an abbreviated alias, because the parser sees it here as the beginning of a string and throws a SyntaxError. Use square brackets to access attributes.
Example
Use rightContext and $'
Var re = / hello/g
Re.test ('hello worldview')
RegExp.rightContext; / / "world!"
RegExp ["$'"]; / / "world!"
LeftContext non-standard attributes are static and read-only properties of regular expressions, with the latest matching left substring. RegExp.$ `is an alias for this property.
Grammar
RegExp.leftContext
RegExp ['$']
Description
The leftContext property is static, not a property of a regular expression independent object. Instead, you should always use it as RegExp.leftContext or RegExp ['$'].
The value of the leftContext property is read-only and is modified when the match succeeds.
You cannot use the property accessor (RegExp.$ `) to use the abbreviated alias, because the parser sees it here as the beginning of the template string and throws a SyntaxError. Use square brackets to access attributes.
Example
Use leftContext and $`
Var re = / world/g
Re.test ('hello worldview')
RegExp.leftContext; / / "hello"
RegExp ['$']; / / "hello"
Standard
Non-standard. Is not part of any current specification.
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