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A regular expression is a logical formula for string operations. It uses predefined characters and combinations of these specific characters to form a "rule string ", this "rule string" is used to express a filtering logic for strings. Regular Expressions are widely used. The following describes the regular expressions in javascript:
Regular Expression Syntax:Syntax 1
Re =/pattern/[flags]
Syntax 2
Re = new Regexp ("pattern", ["Flags"])
Parameters
Re
Required. Name of the variable to be assigned a value in the regular expression mode.
Pattern
Required. The regular expression mode to use. If Syntax 1 is used, use the "/" character separation mode. If syntax 2 is used, quotation marks are used to mark the format.
Flags
Optional. If syntax 2 is used, the flag is enclosed in quotation marks. The flag can be used in combination and available include:
· G (all pattern in full-text search). For example, if you have hundreds of lines of strings to search, you need to add the g id (by default, the JS search range is one line)
· I (Case Insensitive)
· M (multi-line search). By default, JS finds the first matching string to complete any
Example:
Regexp. js
function match() { str1 = "this is JAVA java Java , this is a first RegExp programe!"; //str2 = "java"; re = /java/i; re2 = /java/g; re3 = new RegExp("java", "i"); r = str1.match(re); r2 = str1.match(re2); r3 = str1.match(re3); document.writeln(r); document.writeln(r2); document.writeln(r3);}
Test.html
Register and verify register. jsFunction checkusername () {var username = document. getelementsbyname ("username") [0]. value; // Re = new Regexp ("\ s *", "G"); // Re =/(\ s *)/g // var isempty = Re. test (usrname); var namewarning = ""; if (! (New Regexp ("\ s +"). Test (username) {// determine whether the user name is empty // alert ("Enter the user name! "); Namewarning =" Enter the user name! "; Document. getelementbyid ("namechick "). innertext = namewarning; return false;} document. getelementbyid ("namechick "). innertext = namewarning; return true;} function checkpassword () {var pwdwarning = ""; var Password = document. getelementsbyname ("password") [0]. value; If (password! = ""&&! (New Regexp ("^ (\ s *) $"). Test (password) {// The password is not blank if (! /\ W {6 }/. test (password) {// The password is not a 6-digit character or number pwdwarning = "6-digit character or number ";}} else {// The password is empty pwdwarning = "enter the password! "; Document. getelementbyid ("pwdchick "). innertext = pwdwarning; return false;} document. getelementbyid ("pwdchick "). innertext = pwdwarning; return true;} function checkemail () {var emailwarning = ""; var email = document. getelementsbyname ("email") [0]. value; If (! (New Regexp ("[\ W [. _] + @ [\ W [. _] + \\. [\ W] + ")). test (email) {// The password is not a 6-digit character or number emailwarning = "Incorrect email format! "; // Return false;} document. getelementbyid (" emailchick "). innertext = emailwarning; return true ;}Register.html
<HTML>Success.html
<HTML>
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