Iterating throgh mvc model lists using javascript

Question

I want to iterate through my model values. Following is what I did to achieve this. But the varible count never increments. How can I increment it to iterate throgh my model values?

<script  language="javascript" type="text/javascript">
     function AddStudentName() {

                    var StudentName = document.getElementById('txtStudentName').value;

                    StudentName= StudentName.replace(/^\s+|\s+$/g, '');

                    if(StudentName!= null)
                    {                
                      <%int count = 0; %>
                      for(var counter = 0; parseInt(counter)< parseInt('<%=Model.StudentInfo.Count%>',10); counter++)
                      {
                        alert('<%=count%>');
                        if('<%=Model.StudentInfo[count].StudentName%>' == StudentName)
                        {
                          alert("A student with new student name already exists.");
                          return false;
                        }
                        <%count = count +1;%>
                      }
                    }
                }
    </script>

thanks, Kapil

Daniel Vassallo · Accepted Answer · 2010-05-04 10:04:47Z

1

The code <%count = count + 1;%> will only execute once, on the server-side, when ASP.NET generates the HTML page. That is the reason why it will never increment. You cannot mix logic on server-side and client-side like that.

You can consider building an array in JavaScript filled with the data in Model.StudentInfo[i].StudentName, and then simply iterate through the JavaScript array:

var i;
var studentName = document.getElementById('txtStudentName').value;

// Prepare a 'StudentNamesString' in ASP.NET in the following format:
//
//    ['Student Name 1', 'Student Name 2', 'Student Name 3']
//
// And use it as follows:

var studentNamesOnServer = <%= StudentNamesString; %>;

studentName = studentName.replace(/^\s+|\s+$/g, '');

for (i = 0; i < studentNamesOnServer.length; i++) {
   if (studentNamesOnServer[i] === studentName) {
      alert('A student with new student name already exists.');
   }
}

edited May 4, 2010 at 10:04

answered May 4, 2010 at 9:52

Daniel Vassallo

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4 Comments

Jaqen H'ghar Over a year ago

DO i need to decorate the string items with single quotes?

Jaqen H'ghar Over a year ago

Can i create the StudentNameString on view itself?

Daniel Vassallo Over a year ago

@kapil: Yes, you need to decorate the string items in quotes. However I'm not sure if you can create StudentNameString in the view. I'm not familiar with ASP.NET MVC. But if you can iterate through Model.StudentInfo[i].StudentName in the view, I guess you can.

Daniel Vassallo Over a year ago

Note that you can also use the following in JavaScript: var studentNamesOnServer[]; studentNamesOnServer.push('Name 1'); studentNamesOnServer.push('Name 2'); .... This is instead of initializing the array in 1 line with var studentNamesOnServer = <%= StudentNamesString; %>;

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