text box will not take more than 5 character

//.js file

function Checktextboxlenth(ccNum)
{
var ccno = ccNum.value;
if(ccno.length < 0 || ccno.length >5)
{
alert("length cant acces 5 character");
return false ;
}

return true;
}

////onpageload

btnId1.Attributes.Add("onclick", "Checktextboxlenth(TextBox1)");