text: function addStudent()
      { 
          var rollno=document.sample.rollno.value; 
          var name=document.sample.name.value; 
          
          var tr = document.createElement('tr');
          
          var td1 = tr.appendChild(document.createElement('td'));
          var td2 = tr.appendChild(document.createElement('td'));
          var td3 = tr.appendChild(document.createElement('td'));
          var td4 = tr.appendChild(document.createElement('td'));
          
          
          td1.innerHTML=rollno;
          td2.innerHTML=name;
          td3.innerHTML='<input type="button" name="del" value="Delete" onclick="delStudent(this);" class="btn btn-danger">'
          td4.innerHTML='<input type="button" name="up" value="Update" onclick="UpStud(this);" class="btn btn-primary">'
  
          document.getElementById("tbl").appendChild(tr);
      }
  
      function UpStud(stud){
           var rollno=document.sample.rollno.value; 
          var name=document.sample.name.value; 
          var s = stud.parentNode.parentNode;
          var tr = document.createElement('tr');
          
          var td1 = tr.appendChild(document.createElement('td'));
          var td2 = tr.appendChild(document.createElement('td'));
          var td3 = tr.appendChild(document.createElement('td'));
          var td4 = tr.appendChild(document.createElement('td'));
          
          
          td1.innerHTML='<input type="number" name="rollno1">';
          td2.innerHTML='<input type="text" name="name1">';
          td3.innerHTML='<input type="button" name="del" value="Delete" onclick="delStudent(this);" class="btn btn-danger">'
          td4.innerHTML='<input type="button" name="up" value="Update" onclick="addUpStud(this);" class="btn btn-primary">'
  
          document.getElementById("tbl").replaceChild(tr, s);
      }
  
      function addUpStud(stud){
          var rollno=document.sample.rollno1.value; 
          var name=document.sample.name1.value; 
          var s = stud.parentNode.parentNode;
          var tr = document.createElement('tr');
          
          var td1 = tr.appendChild(document.createElement('td'));
          var td2 = tr.appendChild(document.createElement('td'));
          var td3 = tr.appendChild(document.createElement('td'));
          var td4 = tr.appendChild(document.createElement('td'));
          
          
          td1.innerHTML=rollno;
          td2.innerHTML=name;
          td3.innerHTML='<input type="button" name="del" value="Delete" onclick="delStudent(this);" class="btn btn-danger">'
          td4.innerHTML='<input type="button" name="up" value="Update" onclick="UpStud(this);" class="btn btn-primary">'
  
          document.getElementById("tbl").replaceChild(tr, s);
      }
  
      function delStudent(Stud){
          var s=Stud.parentNode.parentNode;
          s.parentNode.removeChild(s);
      }