Take JavaScript notes (5)-Regular Expression Basics

JavaScript Regular -- RegExp:
RegExp has a test () method. If a given string (with only one parameter) matches this mode, it returns true. Otherwise, it returns false.
Differences and meanings of/I,/g,/ig,/gi,/m in Regular Expressions
/I (case-insensitive)
/G (full-text search for all matching characters)
/M (multi-row search)
/Gi (full-text search, case-insensitive)
/Ig (full-text search, case-insensitive)
[Javascript]
Var str = "jfkd @ s, laj @ fd, safd @ saf, ds @";
Var res = // @/gi; // full-text search @
Alert (res. test (str); // output: true
The exec () method has a string parameter and returns an array. The first entry of the array is the first match, and the rest is the reverse reference.
[Javascript]
// AStr only contains the first instance, which is @ in "jfkd @ sla @
Var aStr = res.exe c (str );
Alert (aStr );
The String object has a match () method, which returns an array containing all matching strings.
[Javascript]
Alert (str. match (res); // output :@,@,@,@
The behavior of another string method called seartch () is similar to that of indexOf (), but it uses a RegExp object rather than just a substring. The Search () method returns a matched position in the string.
[Javascript]
// It starts from the position of the Character index [0]
Alert (str. search (res); // output: 4
Replace ():
[Javascript]
/**
* Replace (), which can replace all the matches of a substring (the first parameter) with another string (the second parameter)
*/
Var sRep = str. replace ("@", "slim horse ");
Alert (sRep); // output: jfkd slim horse s, laj @ fd, safd @ saf, ds @

/**
* You can also use a regular expression as the first parameter.
*/
Alert (str. replace (res, "slim horse"); // output: jfkd slim horse s, laj slim horse fd, safd slim horse saf, ds slim horse


/**
* You can also specify a function as the second parameter of replace.
*/
Var sFun = str. replace (res, function (){
Return "Skinny horse ";
});
Alert ("---------------" + sFun); // output: jfkd, laj, and safd, ds <span> <span class = "comment"> </span>
[Javascript]
/**
* Split ()
*/
Alert (str. split ("@"));
// Use a regular expression to implement the same function
Alert (str. split (/@/));
[Html]
<! -- Example in which a replace method can only be used to process numbers -->
<Input size = "25" value = "" id = "maxnum" name = "tbmeetroom. maxnum" _ cke_saved_name = "tbmeetroom. maxnum"
Onkeyup = "this. value = this. value. replace (/\ D/g ,'')"
Onafterpaste = "this. value = this. value. replace (/\ D/g,'') "/>
All metacharacters in the expression must be escaped (followed by a backslash) to match correctly. Metacharacters are part of the regular expression syntax. Below are all metacharacters used by the regular expression: ([{\ ^ $ | )? * +. Therefore, if you want to match a question mark, then: var reTest = /\? /; Or, var reTest = new RegExp ("\\? "); The second line uses two backslash, called double escape.
Character class:
[Javascript]
<Script type = "text/javascript">
// Simple class -- match "bat", "cat", and "fat"
Var sToMatch = "a bat, a Cat, a fAt baT, a faT cat ";
Var reBatCatRat =/[bcf] at/gi;
Var arrMatches = sToMatch. match (reBatCatRat );
// Alert (arrMatches );

/**
* Negative class: Specifies the characters to be excluded.
* For example, to match all characters except a and B, the character class is [^ AB].
* The escape sign (^) indicates that the regular expression character cannot match the character that follows.
* In the preceding example, if you only want to obtain a word that contains at but cannot start with B or c:
*/
ReBatCatRat =/[^ bc] at/gi;
ArrMatches = sToMatch. match (reBatCatRat );
// Alert (arrMatches );

/**
* Range class-match all the characters in the alphabet, but do not want to input them one by one,
* Available: [a-z]. The hyphen (-) in it indicates "from what to what" (a to z)
* Here, a-z only matches lowercase letters, unless I is used to indicate case insensitive
* If You Want To match only uppercase letters, use: [A-Z]
* Obtains the characters starting with 1, 2, 3, and 4 and starting with number.
*/
SToMatch = "number1, number2, number3, number4, number5, number6, number7, number8, number9 ";
ReBatCatRat =/number [1-4]/gi; // or use negative class/number [^ 5-9]/gi
ArrMatches = sToMatch. match (reBatCatRat );
// Alert (arrMatches );

/**
* Combination class: A character class composed of other classes.
* Assume that you want to match all ~ M letters, numbers from 1 to 4, and a line break
* [A-m1-4 \ n]
* JavaScript/ECMAScript does not support union classes and cross classes in some other regular expressions. This means you cannot have a similar
* [A-m [p-z] or [a-m [^ B-e]
*/


/**
* Pre-defined class
Code is equivalent to matching
. [^ \ N \ r] any character except line feed and carriage return
\ D [0-9] Number
\ D [^ 0-9] non-numeric characters
\ S [\ t \ n \ x0B \ f \ r] blank characters
\ S [^ \ t \ n \ x0B \ f \ r] non-blank characters
\ W [a-zA-Z_0-9] Word characters (all letters, all numbers and underscores)
\ W [^ a-zA-Z_0-9] non-word characters

To match three numbers
*/
SToMatch = "325 fds2 ";
ReBatCatRat =/\ d/; // or use negative class/number [^ 5-9]/gi
Alert (reBatCatRat. test (sToMatch ));
</Script>

From Dan's column