JavaScript form Validation

<! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 transitional//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd ">          <div> Enter your username: </div> <div> <input type= "text" name= "UID" id= "UID" onblur= "Yanzheng ()"/> <span id= "Tishi" ></span> </div> </div > <div> <div> Please enter your password: </div> <div> <i              Nput type= "Password" name= "Uid1" id= "Uid1"/> </div> </div> <div> <div>  Please enter your password again: </div> <div> <input type= "password" name= "Uid2" id= "Uid2" Onblur= "Xiangdeng ()"/> <span id= "Tish2" ></span> </div> </div> <d  Iv> <div> Please enter age: </div> <div> <input type= "text" Name= "Age" id= "Age" onblur= "nage ()"/> <span id= "Tish3" ></span> </div> </d  Iv> <div>      <div> Enter phone number: </div> <div> <input type= "text" name= "t      El "Id=" tel "onblur=" Tell () "/> <span id=" Tish4 "></span> </div> </div> <div> <div> <!--double quotes can be directly written JS code, so you can use return--> <input type= "Submit" Value= "Submit" onclick= "return Check ()"/> </div> </div> </div> </form> </body> &L T;/html> <script>//Perform a click event, execute the Submit function check () {//To determine if the user name is null if no input is present, prompt the user name to be empty and return FALSE if not NULL returns TRU E if (document.getElementById ("UID"). value== "") {alert ("Username cannot be empty!            ");         return false;         }else{return true; }} function Yanzheng () {//non-NULL to verify if (document.getElementById ("UID"). value== "") {//Give             The following span adds text and changes the text color document.getElementById ("Tishi"). innertext= "User name cannot be empty"; Document.getElementbyid ("Tishi"). style.color= "Red";             }else{document.getElementById ("Tishi"). innertext= "User name available";         document.getElementById ("Tishi"). style.color= "Green";         }} function Xiangdeng () {var P1=document.getelementbyid (' Uid1 ');         var P2=document.getelementbyid (' Uid2 ');            Equality validation if (P1.value==p2.value) {document.getElementById ("Tish2"). innertext= "input is correct";         document.getElementById ("Tish2"). style.color= "Green";             }else{document.getElementById ("Tish2"). innertext= "two times input password inconsistent";         document.getElementById ("Tish2"). style.color= "Red";         }} function Nage () {var a = document.getElementById ("Age");             Range validation//get user input values and convert to integers using parseint to compare if (parseint (a.value) >=18 && parseint (a.value) <=50) {             document.getElementById ("Tish3"). innertext= "input is correct";         document.getElementById ("Tish3"). style.color= "Green";  }else{           document.getElementById ("Tish3"). Innertext= "Age does not meet the conditions";         document.getElementById ("Tish3"). style.color= "Red";         }} function tell () {var a = document.getElementById ("tel"); The regular verifies if (A.value.match (/^1[3|4|5|7|8][0-9]{9}$/) ==null) {document.getElementById ("Tish4"). InnerText            = "Mobile phone number is not legal";                                 document.getElementById ("Tish4"). style.color= "Red";            }else{document.getElementById ("Tish4"). innertext= "input is correct";        document.getElementById ("Tish4"). style.color= "Green"; }} </script>

JavaScript Form validation