ES6 - Vapdations

Form vapdation normally used to occur at the server, after the cpent had entered all the necessary data and then pressed the Submit button. If the data entered by the cpent was incorrect or was simply missing, the server would have to send all the data back to the cpent and request that the form be resubmitted with the correct information. This was really a lengthy process which used to put a lot of burden on the server.

JavaScript provides a way to vapdate the form s data on the cpent s computer before sending it to the web server. Form vapdation generally performs two functions.

Basic Vapdation − First of all, the form must be checked to make sure all the mandatory fields are filled in. It would require just a loop through each field in the form and check for data.

Data Format Vapdation − Secondly, the data that is entered must be checked for correct form and value. Your code must include appropriate logic to test the correctness of data.

Example

We will take an example to understand the process of vapdation. Here is a simple form in html format.


<html>
 
   <head> 
      <title>Form Vapdation</title> 
      <script type = "text/javascript"> 
         <!--  
            // Form vapdation code will come here.  
            //
         --> 
      </script> 
   </head> 

   <body> 
      <form action = "/cgi-bin/test.cgi" name = "myForm" onsubmit = "return(vapdate());"> 
         <table cellspacing = "2" cellpadding = "2" border = "1"> 
            <tr> 
               <td apgn = "right">Name</td> 
               <td><input type = "text" name = "Name" /></td>
            </tr> 
            <tr> 
               <td apgn = "right">EMail</td> 
               <td><input type = "text" name = "EMail" /></td> 
            </tr> 
            <tr> 
               <td apgn = "right">Zip Code</td> 
               <td><input type = "text" name = "Zip" /></td> 
            </tr> 
            <tr> 
               <td apgn = "right">Country</td> 
               <td> 
                  <select name = "Country"> 
                     <option value = "-1" selected>[choose yours]</option> 
                     <option value = "1">USA</option> 
                     <option value = "2">UK</option> 
                     <option value = "3">INDIA</option> 
                  </select> 
               </td> 
            </tr> 
            <tr> 
               <td apgn = "right"></td> 
               <td><input type = "submit" value = "Submit" /></td> 
            </tr> 
         </table> 
      </form> 
   </body> 
   
</html>

Output

The following output is displayed on successful execution of the above code.

Basic Form Vapdation

First let us see how to do a basic form vapdation. In the above form, we are calpng vapdate() to vapdate data when onsubmit event is occurring. The following code shows the implementation of this vapdate() function.


<script type = "text/javascript"> 
   <!--  
      // Form vapdation code will come here. function vapdate() {    
         if( document.myForm.Name.value == "" ) {  
            alert( "Please provide your name!" );      
            document.myForm.Name.focus() ;      
            return false;  
         }  
         if( document.myForm.EMail.value == "" ) {  
            alert( "Please provide your Email!" );      
            document.myForm.EMail.focus() ;      
            return false; 
         }  
         if( document.myForm.Zip.value == "" ||            
         isNaN( document.myForm.Zip.value ) ||            
         document.myForm.Zip.value.length != 5 ) {  
            alert( "Please provide a zip in the format #####." );      
            document.myForm.Zip.focus() ;      
            return false;  
         }  
         if( document.myForm.Country.value == "-1" ) {  
            alert( "Please provide your country!" );      
            return false;  
         }  
         return( true );  
      }  
      //
   --> 
</script>

Data Format Vapdation

Now we will see how we can vapdate our entered form data before submitting it to the web server.

The following example shows how to vapdate an entered email address. An email address must contain at least a ‘@’ sign and a dot (.). Also, the ‘@’ must not be the first character of the email address, and the last dot must at least be one character after the ‘@’ sign

Example

Try the following code for email vapdation.


<script type = "text/javascript"> 
   <!--  
      function vapdateEmail() { 
         var emailID = document.myForm.EMail.value;    
         atpos = emailID.indexOf("@");    
         dotpos = emailID.lastIndexOf(".");    
         
         if (atpos < 1 || ( dotpos - atpos < 2 )) {       
            alert("Please enter correct email ID")         
            document.myForm.EMail.focus() ;         
            return false;    
         }     
         return( true );  
      } 
      //
   --< 
</script>

ES6 - Vapdations

Example

Output

Basic Form Vapdation

Data Format Vapdation

Example

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