javascript validation for textboxes checkbox and listbox in gridview

function ValidateGrid()
{
txtempName = document.getElementById('<%=((TextBox)GridView1.FooterRow.FindControl("txtempName")).ClientID%>');
txtempcode = document.getElementById('<%=((TextBox)GridView1.FooterRow.FindControl("txtempcode")).ClientID %>');
DropDownList2 = document.getElementById('<%=((DropDownList)GridView1.FooterRow.FindControl("DropDownList2")).ClientID%>');
txtsalary = document.getElementById('<%=((TextBox)GridView1.FooterRow.FindControl("txtsalary")).ClientID %>');
//listItemArray = document.getElementById('<%=((RadioButtonList)GridView1.FooterRow.FindControl("RadioButtonList2")).ClientID %>');

if(txtempName.value == 0)
{
alert("Please enter name...!");
txtempName.focus();
return false;
}
if(txtempcode.value == 0)
{
alert("Please Enter Emp code...!");
txtempcode.focus();
return false;
}
var str='';

var Grid_Table = document.getElementById('<%= GridView1.ClientID %>');
var SearchText = document.getElementById('<%=((TextBox)GridView1.FooterRow.FindControl("txtempcode")).ClientID %>').value;
var lenth =Grid_Table.rows.length;
if(lenth > 3)
{
for(var row=1; row<Grid_Table.rows.length-1; row++)
{
for(var col=0; col<Grid_Table.rows[row].cells.length; col++)
{
if(col==0)
 if(document.all[col])
  str=str+Grid_Table.rows[row].cells[2].innerText;
}
} 
}          str=str+'\n'; 
   var array=str.split(" "); 
   for(i = 0; i < array.length; i ++)

{ 

if(array[i] == SearchText)
{
//break;
alert("empcode  already exist");
return false;
}
}
if(DropDownList2.value == 0)
{
alert("Please select ...!");
DropDownList2.focus();
return false;
}
if(txtsalary.value == 0)
{
alert("Please Enter salary...!");
txtsalary.focus();
return false;
}
var numericExpression = /^[0-9]+$/;
if(txtsalary.value.match(numericExpression)){
return true;
}else{
alert("enter Number only");
txtsalary.focus();
return false;
}
var BaseControl = null;
BaseControl = document.getElementById('<%= this.GridView1.ClientID %>');
if (BaseControl == null)
return false;           
var ChildControl = "CheckBoxList1";
var Inputs = BaseControl.getElementsByTagName("input");
for (var n = 0; n < Inputs.length; ++n)
 if (Inputs[n].type == 'checkbox' && Inputs[n].id.indexOf(ChildControl, 0) >= 0 && Inputs[n].checked)
  var valid= true;
if(!valid)
{
alert('Select at least one Skill..!');
 return false;
 
}

var grid = document.getElementById('<%= GridView1.ClientID %>');
var rlength=grid.rows.length;
var clength=rlength-1;
var proj=grid.rows[clength].cells[7].childNodes[0];
for(i = 0; i < proj.length; i++) 
{
if(proj[i].selected)
{
var isvalid=true;
break;
}
    }
if(!isvalid){
alert("select atleast one project..! "); 
return false;
}
return true;
}