javascript-Regular Expressions

Introduction to Regular expressions

set of Rule Expressions

1. Application Scenarios for regular expressions

Form Validation

parsing URL parameters

Filter ....

2. Definition of regular expressions

literal form === " //

constructor Form === " new RegExp ()

difference

cannot put variables in literal form | function

variables can be placed in the form of constructors | function

/* var reg =/a/;alert (reg); */ var New REGEXP ("B"); alert (reg);

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3. Methods of Regular expressions

Test :

Function: see if the content matches the regular

return : boolean value

match = ="true "

does not match ===>false

exec

Function: see if the content matches the regular

Return: array of matched contents

Array of match = =

do not match = ="null "

/* var reg =/a/;var str = "a"; Alert (  reg.test (str));   Truealert (typeof reg.exec (str));  Object Delete typeof returns a*/var num1 =1  ; // var reg1 =/"+num1+"/;   var New RegExp (NUM1);    var str1 = "1";    // alert (REG1);//"+num1+"/   Alert (Reg1.test (STR1)  //true

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Second, the meta-character of the regular expression

"= = ="matches any "one" character in parentheses

[^] = = =matches any character except in parentheses

[0-9] = = =matches any number from 0 to 9

[A-z] = = =matches Any lowercase letter a to z

[A-z] = = =matches any uppercase letter a to Z

\d = = =number of matches:[0-9]

\d = = ="matches non-digital

\w = = ="matches numbers, letters, underscores : [0-9a-za-z_]

\w = = =matches non-digits, letters, underscores

\s = = ="Match spaces

\s = = ="non-whitespace"

\b = = ="Match boundary"

  . = = =Any character other than line break

Escape character

\ = = Removes the special meaning of the metacharacters function, such as \d's matching number function \\d added escape after it becomes true D and loses the matching number function

/*var reg =/[abc]/;//matches any one of the characters within the brackets var str = "C"; Alert (Reg.test (str)); True*//*var reg1 =/[^abc]/;var str1 = "U"; alert (Reg1.test (STR1));//true*//*var reg2 =/[3-9]/;var num2 = 5;alert (Reg2.test (num2));//true*///var reg3 =/[a-z]/;/*var reg3 =/[a-z]/;var Str3 = "A"; Alert (Reg3.test (STR3));//true*///var reg4 =/[0-9a-za-z]/; Numeric Case Letters//var reg1 =/\d/;/*var reg1 =/\d/;var Num1 = 5;alert (Reg1.test (NUM1));*///var reg2 =/\w/;/*var reg2 =/\w/;var str2 = "_"; Alert (Reg2.test (STR2));*///var reg3 =/\s/;/*var reg3 =/\s/;var Str3 = ""; Alert (Reg3.test (STR3));*//*var reg4 =/\ba/;var STR4 = "a"; Alert (Reg4.test (STR4));*//*var reg5 =/./;var STR5 = "\ n"; Alert (Reg5.test (STR5));*/varReg6 =/\./;//there is a special meaning, any character other than the line breakvarSTR6 = "."; alert (Reg6.test (STR6));

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Third, regular expression qualifier

^ = = = Startswith the string ( start )

$= =to end of string ( end )

/* var reg =/\d/;//  \d ====> number  no qualifier num, as long as there is a number can be var num = "5a"; alert (num); */ /* var reg1 =/\w/;//  alphanumeric   underscore var str1 = "^_^"; Alert (  reg1.test (str1)); */ /* var reg2 =/^\d\d$/;  Start with a number with   a number ending  = = = "number only one number var num2 =" "; Alert (Reg2.test (num2)  ); */

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Iv. Recurrence of regular expressions

{n} ====> match repeats n times

{n,} = =match repeats at least n times, up to No limit

{n,m} = ="Match repeats at least n times, up to m times

* = =The match repeats at least 0 times, Maximum unlimited

+ = ="Match repeat at least 1 times, Maximum unlimited

? = = ="Match repeats at least 0 times, up to one time

/*var reg3 =/^\d{11}$/;//Mobile number ===>11 number of bits var num3 = 1234567890;alert (Reg3.test (num3));//false*///match numbers match to a minimum of 6 times, up to No limit/*var reg4 =/^\d{6,}$/;var STR4 = "123454655555555555789"; Alert (Reg4.test (STR4))*///User name minimum of 6 characters, maximum of 12 characters/*var reg5 =/^\w{6,12}$/;var STR5 = "123ab__44444a"; Alert (Reg5.test (STR5));*//*var reg6 =/^\d*$/;//matches the number, at least not, no limit var num6 = ""; Alert (Reg6.test (NUM6));*//*var Reg7 =/^\d+$/;//matches the number, at least once, without limiting var num7 = "1111111111111"; Alert (Reg7.test (NUM7));*//*var Reg8 =/^\d?$/;//matches the number, at least 0 times, at most once var num8 = "one"; Alert (Reg8.test (NUM8));*/

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Five, selectors

| = = ="or

var reg1 =/com|cn/; var str1 = "com"; alert (  //COM or CN is true

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six, modifier

I = = = Case insensitive

g = =Full text match (global mode)

m = = =line break match

/*var reg1 =/[a-za-z]/; Matches uppercase letters, matches the lowercase letter var str1 = "A"; Alert (Reg1.test (STR1));*//*var reg1 =/[a-z]/i; i=== "case-insensitive var str1 =" B "; alert (Reg1.test (STR1));*//*var reg1 = new RegExp ("[A-Z]", "I"), var str1 = "B"; alert (Reg1.test (STR1));*//*var reg1 =/a/g;var str1 = "abc a A"; var str = str1.replace (REG1, "#");d ocument.write (str);*//*var reg1 =/baidu/g;var str1 = "1.baidu\n2.baidu\n3.baidu"; var str = str1.replace (REG1, "#");d ocument.write (str);*//*var reg1 =/^\d/gm;var str1 = "1.baidu\n2.baidu\n3.baidu"; var str = str1.replace (REG1, "#");d ocument.write (str);*/varREG2 =/[a-z]/IgM;varSTR2 = "A A A a a a";varstr = str2.replace (REG2, "#");d ocument.write (str);

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Vii. Grouping

() = ="Combine the contents."

/* var reg1 =/^ (ABC) $/;var STR1 = "abc"; Alert (Reg1.test (STR1)  ); */ /* var reg2 =/^ab{3}c{3}$/;  C Repeat must be 3 times    var str2 = "ABBBCCC";    Alert (  reg2.test (str2)  ); */ /* var reg2 =/^ (ABC) {3}$/;  The ABC repetition must be 3 times var str2 = "abcabcabc"; Alert (  reg2.test (str2)  ); */

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Eight, character class

Regexp. (Dollar) $ ... (dollar)

Attention:

To use a character class, you must use the regular

To return results using the character class, you must have a grouping in the regular

/* var reg1 =/(a)/;var str1 = "ABC abc abc"; Reg1.test (str1); alert (  regexp.$1  );//Match to content within the first group */  / *var reg2 =/(Baidu) (Taobao) (JD)/;var str2 = "Baidu taobao JD"; Reg2.exec (str2);//Run regular alert (      Regexp.$3       ); */ var reg3 =/(taobao)/; var str3 = "I am Taobao"; var str = str3.replace (reg3, "<b style= ' color:red ' >$1</b>");d ocument.write (str);

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Nine, string matching regular method

Search

If the match function subscript position

if it does not match return -1

Global not supported * * * *

Match

If the match returns an array

if the mismatch returns null

Match and exec differences

Match supports global

EXEC does not support global and can be traversed with loops

Replace

syntax: String . Method Name

/*var reg1 =/a/g;var str1 = "B A c a D"; var sh = str1.search (REG1);d ocument.write (SH);*//*var reg2 =/a/g;var str2 = "ab ac ad";//var arr = reg2.exec (STR2); Regular. exec this method = = "Does not support global//document.write (arr); var arr = Null;while (arr=reg2.exec (str2)) {document.write (arr);}*//*var reg3 =/a/g;var STR3 = "ab ac ad"; var arr = Str3.match (reg3);d ocument.write (arr);*/varREG4 =/b/G;varSTR4 = "AB BB cb";varstr = str4.replace (REG4, "*");d ocument.write (str);

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javascript-Regular Expressions