这两个JS函数是干嘛用的

Question

function createXHR()
{
if(typeof XMLHttpRequest != 'undefined')
{
return new XMLHttpRequest;
}
else(typeof ActiveXObject != 'undefined') //under IE7
    {
        if(typeof arguments.callee.ActiveXObject != 'string')
        {
            var o = ['MSXML2.XMLHttp.6.0','MSXML2.XMLHttp.3.0','MSXML2.XMLHttp'];
            for(var i=0,len=o.length;i<len;i++)
            {
                try
                {
                    xhr = new ActiveXObject(o[i]);
                    arguments.callee.ActiveXObject = o[i];
                    return xhr;
                }
                catch(e)
                {
                    //alert('f');
                }
            }
        }
        return new ActiveXObject(arguments.callee.ActiveXObject);
    }
    return xhr;
}
function vote(id)
{
    var xhr = createXHR();
    xhr.onreadystatechange = function(){
        if(xhr.readyState==4)
        {
            if((xhr.status>=200 && xhr.status<300) || xhr.status==304)
            {
                //alert(xhr.responseText);return;
                if(xhr.responseText==1){
                    alert('投票已过期!!');
                }
                else if(xhr.responseText==2){
                    alert('投票数太多，请稍后再投!!');
                }
                else if(xhr.responseText==3){
                    var v = parseInt(document.getElementById('pic_'+id).innerHTML);
                    document.getElementById('pic_'+id).innerHTML = v+1;
                    alert('投票成功!!');
                }
            }
        }
    };
 
    xhr.open('POST','vote.php',true);
    xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
    xhr.send('id='+id);
}
调用的时候是vote(1)
    xhr.open('POST','vote.php',true);
    xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
    xhr.send('id='+id);
是用来post发送数据的。那前面是差不多干嘛用的？

Answer 1

function createXHR()是用来创建一个ajax对象的，不明白的话看看ajax介绍：
http://www.w3school.com.cn/ajax/index.asp

Answer 2

创建 XMLHttpRequest  对象