js xmlHttpRequest

var xhr =window.XMLHttpRequest?new XMLHttpRequest():new ActiveXObject("Microsoft.XMLHTTP");
if(xhr){
xhr.onreadystatechange = function(){
if (this.readyState == 4 && this.status == 200){
//对返回数据的处理，下例为json类型
var objJson = eval("(" + this.responseText + ")");
for( i = 0; i < objJson.geoList.length; i++) {
var item= objJson.geoList[i];
}

}
};
var urlStr = "url?paras";
xhr.open("GET", urlStr);
xhr.send();
}