【急】iframe父操作子的dom元素失效?

父级:

 <!doctype html>
<html>
 <head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
  <meta name="Generator" content="EditPlus®">
  <meta name="Author" content="">
  <meta name="Keywords" content="">
  <meta name="Description" content="">
  <title>Document</title>
  <script src="js/jquery-1.11.3.js"></script>
  <style>
    * {padding: 0; margin: 0;}
    body,html {width: 100%; height: 100%;}
  </style>
 </head>
 <body>
    <iframe id="qq" name="myFrame" src="test2.html" frameborder="0"></iframe>
 </body>

 <script>

    ;$(function() {
        var x = document.getElementById('qq').contentWindow.document.getElementById('div1');

        console.log(x);

    });




 </script>
</html>

子级:

 <!doctype html>
<html>
 <head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
  <meta name="Generator" content="EditPlus®">
  <meta name="Author" content="">
  <meta name="Keywords" content="">
  <meta name="Description" content="">
  <title>Document</title>
  <script src="js/jquery-1.11.3.js"></script>
  <style>
    * {padding: 0; margin: 0;}
    body,html {width: 100%; height: 100%;}
  #div1 {height: 200px; background: red;}
  </style>
 </head>
 <body>
    <div id="div1">123</div>
 </body>

 <script>

    $(function() {


    })




 </script>
</html>

请问为什么输出的null???
我想操作iframe里面的元素,求解决?

如果换成:
var x = $(window.frames["myFrame"].document).find("#div1").text();
console.log(x);
输出的是空值,不知道问题到底出在哪里??网上教程对不对啊

http://blog.jjonline.cn/userInterFace/140.html

$(function(){...})是父页dom对象好了就执行,iframe不一定加载完毕,改为$(window).load

 $(window).load(function() {
        var x = document.getElementById('qq').contentWindow.document.getElementById('div1');

        console.log(x);

    });

父级页面js:

            function getChildEle() {```
            var x = document.getElementById('qq').contentWindow.document.getElementById('div1');
            console.log(x);
            }

子级页面JS:
$(function() {
window.top.getChildEle();
});


父级页面js:

        function getChildEle() {```
        var x = document.getElementById('qq').contentWindow.document.getElementById('div1');
        console.log(x);
        }

子级页面JS:
$(function() {
window.top.getChildEle();
});

var x = $('#div1', window.iframes['iframename'].document)

你酱紫肯定要失败了,浏览器是有安全性约束的,如果在一个A域的页面内嵌一个B域的,而且A还要通过代码去访问B的内容,这就是所谓的XSS(Cross Site Script)夸域攻击了。