Javascript validation for Gridview in edit mode

 Javascript validation for Gridview textbox in edit mode  
 Clientside validation for Gridview textboxex while edting record.  
 Here gridview have dropdownlist and two textbox.This javascript clientside code validate these fields while edting record.   
 function ValidateGridEditMode()  
 {  
      var Gid = document.getElementById('ctl00_ContentPlaceHolder1_TabContaner_tabCustomer_gvCustomer').rows.length;  
      var i;  
      for(i=2; i <=Gid; i++)  
      {   
           if(i<10)  
           {  
                ddlCustLocation = document.getElementById('ctl00_ContentPlaceHolder1_TabContaner_tabCustomer_gvCustomer_ctl0'+i+'_ddlCustLocation');  
                txtCustCode = document.getElementById('ctl00_ContentPlaceHolder1_TabContaner_tabCustomer_gvCustomer_ctl0'+i+'_txtCustCode');  
                txtCustName = document.getElementById('ctl00_ContentPlaceHolder1_TabContaner_tabCustomer_gvCustomer_ctl0'+i+'_txtCustName');   
           }  
           else  
           {  
                ddlCustLocation = document.getElementById('ctl00_ContentPlaceHolder1_TabContaner_tabCustomer_gvCustomer_ctl'+i+'_ddlCustLocation');  
                txtCustCode = document.getElementById('ctl00_ContentPlaceHolder1_TabContaner_tabCustomer_gvCustomer_ctl'+i+'_txtCustCode');  
                txtCustName = document.getElementById('ctl00_ContentPlaceHolder1_TabContaner_tabCustomer_gvCustomer_ctl'+i+'_txtCustName');   
           }  
           ddlCustLocation != null || txtCustCode != null || txtCustName != null)  
           {  
                ddlCustLocation == 0)  
                {  
                     alert("Please Select Location..");  
                     ddlCustLocation.focus();  
                     return false;  
                }   
                else  
                {  
                     if(txtCustCode.value == 0)  
                     {  
                          alert("Please enter Customer Code..");   
                          txtCustCode.focus();   
                          return false;  
                     }   
                     else  
                     {  
                          if(txtCustName.value == "")  
                          {  
                               alert("Please enter Customer Name ..");   
                               txtCustName.focus();   
                               return false;  
                          }  
                     }   
                }   
           }   
      }  
      return true;  
 }