无需ActiveX支持的Ajax之IE实现

/*
coded by Kae - http://verens.com/
use this code as you wish, but retain this notice
*/

function XMLHttpRequest() {
    var i=0;
    var url='';
    var responseText='';
    this.onreadystatechange=function(){
        return false;
    }
    this.open=function(method,url){
        //TODO: POST methods
        this.i=++kXHR_instances; // id number of this request
        this.url=url;
        var iframe=document.createElement('<iframe id="kXHR_iframe_'+this.i+'" type="text/plain" style="display:none"></iframe>');
        document.body.appendChild(iframe);
    }
    this.send=function(postdata){
        //TODO: use the postdata
        var el=document.getElementById('kXHR_iframe_'+this.i);
        el.src=this.url;
        kXHR_objs[this.i]=this;
        setTimeout('XMLHttpRequest_checkState('+this.i+')',500);
    }
    return true;
}
function XMLHttpRequest_checkState(inst){
    var el=document.getElementById('kXHR_iframe_'+inst);
    if(el.readyState=='complete'){
        var responseText=window.frames['kXHR_iframe_'+inst].document.body.childNodes[0].data;
        kXHR_objs[inst].responseText=responseText;
        kXHR_objs[inst].readyState=4;
        kXHR_objs[inst].status=200;
        kXHR_objs[inst].onreadystatechange();
        el.parentNode.removeChild(el);
    }else{
        setTimeout('XMLHttpRequest_checkState('+inst+')',500);
    }
}
var kXHR_instances=0;
var kXHR_objs=[];