js实现网页防止被iframe框架嵌套及几种location.href的区别

首先我们了解一下：window.location.href、location.href、self.location.href、parent.location.href、top.location.href他们的区别与联系，简单的说：几种location.href的区别 js实现网页被iframe框架功能 
"window.location.href"、"location.href"、"self.location.href"是本页面跳转 
"parent.location.href"是上一层页面跳转 
"top.location.href"是最外层的页面跳转 

举个例子说明（如上图）： 
如果A,B,C,D都是普通页面，D是C的iframe，C是B的iframe，B是A的iframe， 
如果D中js这样写： 
"window.location.href"、"location.href"：D页面跳转 
"parent.location.href"：C页面跳转 
"top.location.href"：A页面跳转 

如果D页面中有form的话： 

<script language="javascript"> 
if(top.location!==self.location){ 
WarningTxt1 = "content页面被iframe了！"; 
WarningTxt2 = "我们跳出iframe，直接访问content页面吧！"; 
alert(WarningTxt1); 
alert(WarningTxt2); 
top.location.href=self.location.href; 
} 
</script>