js动态创建控件附加事件失效问题

问题：
            tb为一个table
            var row = tb.rows[0];
            var cell=row.insertCell(row.cells.length);
            cell.innerHTML = "aaaa";
            cell.style.display = "";
            cell.style.cursor = "pointer";
            cell.onmouseover = "mOver(this)";
            cell.onmouseout = "mOut(this)";
            cell.onclick = "mClick(this)";

以上是在一个table中加一个单元格 但是
            cell.onmouseover = "mOver(this)";
            cell.onmouseout = "mOut(this)";
            cell.onclick = "mClick(this)";
却无效

也就是说在动态添加的单元格上的事件 无效

解决方法：用eval()函数

            cell.setAttribute("onmouseover", eval(function(){mOver(this)}));
            cell.setAttribute("onmouseout", eval(function(){mOut(this)}));
            cell.setAttribute("onclick", eval(function(){mClick(this)}));