js 动态增加表格

function insRow(){
		
	document.getElementById("rowId").value=parseInt(document.getElementById("rowId").value)+1;
		
	var rowId = document.getElementById("rowId").value;

	var tb1 = document.getElementById("ctable");

var rowsCount=tb1.rows.length;

var row = tb1.insertRow(rowsCount);

var cell = row.insertCell(0);  
    cell.innerHTML="<img src=\"<%=contextPath%>/img/update.gif\" class=\"nav\" />";    
	 var cell = row.insertCell(1); 
    cell.innerHTML="<input name=\"companyname"+rowId+"\" ID=\"companyname"+rowId+"\" type=\"text\" />";
    var cell = row.insertCell(2); 
    cell.innerHTML="<input name=\"companynameen"+rowId+"\" ID=\"companynameen"+rowId+"\" type=\"text\"  />";
}