原生ajax

function toData(obj) {
    if(obj == null) {
        return obj;
    }
    var arr = [];
    for(var i in obj) {
        var str = i + "=" + obj[i];
        arr.push(str);
    }
    return arr.join("&");
}

function ajax(obj) {
    //指定提交方式的默认值
    obj.type = obj.type || "get";
    //设置是否异步，默认为true(异步)
    obj.async = obj.async || true;
    //设置数据的默认值
    obj.data = obj.data || null;
    if(window.XMLHttpRequest) {
        //非ie
        var ajax = new XMLHttpRequest();
    } else {
        //ie
        var ajax = new ActiveXObject("Microsoft.XMLHTTP");
    }
    //区分get和post
    if(obj.type == "post") {
        ajax.open(obj.type, obj.url, obj.async);
        ajax.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
        var data = toData(obj.data);
        ajax.send(data);
    } else {
        //get  test.php?xx=xx&aa=xx
        var url = obj.url + "?" + toData(obj.data);
        ajax.open(obj.type, url, obj.async);
        ajax.send();
    }

    ajax.onreadystatechange = function() {
        if(ajax.readyState == 4) {
            if(ajax.status >= 200 && ajax.status < 300 || ajax.status == 304) {
                if(obj.success) {
                    obj.success(ajax.responseText);
                }
            } else {
                if(obj.error) {
                    obj.error(ajax.status);
                }
            }
        }
    }

}