/*异步传输json strData的数据如:name=value&name1=value1&name2=value2*/
function loadJson(method, url, strData, f, async) {
if (typeof (async) == "undefined") async = true;
var xr = new XMLHttpRequest();
xr.onreadystatechange = function(){
if(this.readyState == 4){
if(this.status == 200 && this.responseText != ""){
if(typeof(f) === 'function')
f(eval('('+this.responseText+')'));
}
}
}
xr.open(method, url, async);
if(method.toLowerCase() == 'post')
xr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
xr.send(strData);
}