Add or delete lines of table by JS

When want to add a line or delete a line for detailed info for basic object ,we can use this:

function deleteRow(tableObjStr,saveNumber){
    var tableObj = document.getElementById(tableObjStr);
    var rowNum   = tableObj.rows.length-1;
    var count = 0;
    if(rowNum==1)  return alert("Cannot delete anymore!");
    for(var i=document.zzjcdForm.checkbox.length-1;i>=1;i--)
    {
      if(document.zzjcdForm.checkbox[i].checked)
      {
        count++;
        tableObj.deleteRow(i+1); 
       }
    }
     if(count==0)alert("Pls select the line u want to delete !");       
}

// add a line
function addRow(tableObjStr,tr0,trIdPrefix){
var tableObj = document.getElementById(tableObjStr);
var trNode     = document.getElementById(tr0);
var trObj    = trNode.cloneNode(true);
var rowNum   = eval(tableObj.lastChild.lastChild.id.substring(tableObj.lastChild.lastChild.id.indexOf(trIdPrefix)+trIdPrefix.length));
tableObj.lastChild.appendChild(trObj);
tableObj.lastChild.lastChild.id=trIdPrefix+(rowNum+1);
tableObj.lastChild.lastChild.style.display=""; 
}