javascript在OPERA中不起作用

这个javascript可以在Firefox、IE、Chrome中使用,但不能在Opera中使用。如何使其跨浏览器兼容? 我需要脚本来检测点击iframe。

<script>
var isOverIFrame = false;
function processMouseOut() {
isOverIFrame = false;
top.focus();
}
function processMouseOver() { isOverIFrame = true; }
function processIFrameClick() {
if(isOverIFrame) {
//was clicked
}
}

function init() {
var element = document.getElementsByTagName("iframe");
for (var i=0; i<element.length; i++) {
    element[i].onmouseover = processMouseOver;
    element[i].onmouseout = processMouseOut;
}
if (typeof window.attachEvent != 'undefined') {
    top.attachEvent('onblur', processIFrameClick);
}
else if (typeof window.addEventListener != 'undefined') {
    top.addEventListener('blur', processIFrameClick, false);
}
}
</script>

<iframe src="http://google.com"></iframe>

<script>init();</script>