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Javascript - Validations
  • 时间：2024-09-17

JavaScript - Form Vapdation

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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 a 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 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 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 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