(Multi) select list box - selected parameters check

sunsolaris2000

20 New Member

I have 2 list boxes in SCAssignment.jsp. One is multi select, one single select.

I use it because user will input how 'students' are assigned to 'courses'.

I want to alert the user to select '1 student to 1/many courses' per form entry. These relations I will enter to the bridge table, "students_courses".

I've seen many examples on forums and Google but none didn't work for me :( I think the problem is when I call the JavaScript function.

This is one variant I used, adapted to my sch. project:

[.....................]

Expand|Select|Wrap|Line Numbers

 <html>

   <head>

      <script language="javascript">
 
            function validateListBox(){

                var lb = document.getElementById('mySelect');

                var count1 = 0;

                arrTexts = new Array();
 
                for(var i=0; i<lb.length; i++)  {

                    if(lb[i] != 0){

                      count1++;

                    }
 
                }
 
                if(count1 != 0){

                    alert('empty');

                    return true;

                }
 
                return false;        

            }
 
          </script>

          <noscript>Your browser does not support JavaScript!</noscript>

     </head>

[.......................................]
 
       <form action = "AssignmentsList.jsp" method="post" name="entry">
 
                [.....................]

              <select id = "mySelect" multiple name = "mySelect" size = "5">

                       <% for (Student st : students){%>

                             <option value="<%= st.getStudent_id() %>"><%= st.getStudent_id() %></option>

                                <%}%>

                         </select>                
 
                 [...................]

                           <input type="button" value = "Link" onClick = "validateListBox()"/>

                           <br>

                           <input type = "reset" value = "Reset"/>

                      [...................]

                          <select  id = "mySelect2" name = "mySelect2" size = "5">

                              <% for (Course cs : courses){%>

                                    <option value="<%= cs.getCourse_id() %>"><%= cs.getCourse_id() %></option>

                               <%}%>

                          </select>

                  [...................]    
 
             </form>

             [.............]            
 
          </body>

</html>

They are displayed in a table so I cut the code a bit with [.....].

I tried with onClick, onSubmit, input type="button", input type="submit", what I've seen by now.

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Jul 16 '12 #1

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2720

sunsolaris2000

New Member

I finally find out is:

Expand|Select|Wrap|Line Numbers

 <script language="javascript">
 
            function validate(){

                var k=0;

                if (entry.elements["sid"].selectedIndex == -1) {

                      k++;

                      alert('You cannot select one side only');

                      return false;

                }
 
                if (entry.elements["cid"].selectedIndex == -1) {

                      k++;

                      alert('You cannot select one side only');

                      return false;

                }
 
                if(k == 0){

                  return true;

                }
 
                return false;

            }
 
          </script>

Jul 22 '12 #2

sunsolaris2000

New Member

I found it out finally:

Expand|Select|Wrap|Line Numbers

 <script language="javascript">
 
            function validate(){

                var k=0;

                if (entry.elements["sname"].selectedIndex == -1) {

                      k++;

                      alert('You cannot select one side only');

                      return false;

                }
 
                if (entry.elements["ctitle"].selectedIndex == -1) {

                      k++;

                      alert('You cannot select one side only');

                      return false;

                }
 
                if(k == 0){

                  return true;

                }
 
                return false;

            }
 
          </script>

Jul 27 '12 #3

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