Ajax垮浏览器的写法－－抛绣球方式

if (window.ActiveXObject && !window.XMLHttpRequest)
{
    window.XMLHttpRequest = function() {
    var MSXML = ['Msxml2.XMLHTTP.5.0','Msxml2.XMLHTTP.4.0','Msxml2.XMLHTTP.3.0','Msxml2.XMLHTTP','Microsoft.XMLHTTP'];
    for (var i = 0; i < MSXML.length; i++)
    {
    try {

//----------------------这里就是抛绣球咯
            return new ActiveXObject(MSXML[i]);
        } catch (e) {}
}
return null;
};
}