js 获取子节点函数 (兼容FF与IE)

代码如下:
function getFirstChild(obj) {
var result = obj.firstChild;
while (!result.tagName) {
result = result.nextSibling;
}
return result;
}

function getNextChild(obj) {
var result = obj.nextSibling;
while (!result.tagName) {
result = result.nextSibling;
}
return result;
}