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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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