js 绑定带参数的事件以及手动触发事件

<div>
<div id="tab">
<h2>标题一</h2>
<h2>标题二</h2>
<h2>标题三</h2>
<h2>标题四</h2>
div>
<dl id="tabcon">
<dd>内容一</dd>
<dd>内容二</dd>
<dd>内容三</dd>
<dd>内容四</dd>
</dl>
<div>

<script type="text/javascript" defer="defer">
var tab = document.getElementById("tab").getElementsByTagName("h2");
function swap(n) {
return function() {
for(var i=0; i<tab.length; i++) {
document.getElementById("tabcon" + i).style.display = "none";
document.getElementById("tab" + i).className = "";
}
document.getElementById("tabcon" + n).style.display = "block";
document.getElementById("tab" + n).className = "focus";
}
}

for(var i=0; i<tab.length; i++) {
tab[i].setAttribute("id", "tab" + i);
if(window.addEventListener) {
tab[i].addEventListener("mouseover", swap(i), false);
} else if(window.attachEvent) {
tab[i].attachEvent("onmouseover", swap(i));
}
}

var tabcon = document.getElementById("tabcon").getElementsByTagName("dd");
for(i=0; i<tabcon.length; i++) {
tabcon[i].setAttribute("id", "tabcon" + i);
}

if(document.createEvent) {
var evObj = document.createEvent('MouseEvents');
evObj.initEvent( 'mouseover', true, false);
tab[0].dispatchEvent(evObj);
} else if( document.createEventObject) {
tab[0].fireEvent('onmouseover');
}
</script>