关于Ajax连接池

很多时候Ajax的xmlHttpRequest请求都不是并发的,所以可以直接在JS中调用,或者调用jquery中的方法即可;
但是如果考虑到请求并发的情况,而且时间比较长并且频率也比较高,就需要考虑连接池问题了;
下面是Ajax连接池代码:

---

code:

var XMLHttp = {
    _objPool: [],
    _getInstance: function() {
        for (var i = 0; i < this._objPool.length; i++) {
            if (this._objPool[i].readyState == 0 || this._objPool[i].readyState == 4) {
                return this._objPool[i];
            }
        }
        // IE5中不支持push方法
        this._objPool[this._objPool.length] = this._createObj();
        return this._objPool[this._objPool.length - 1];
    },
    _createObj: function() {
        if (window.XMLHttpRequest) {
            var objXMLHttp = new XMLHttpRequest();
        }
        else {
            var MSXML = ['MSXML2.XMLHTTP.5.0', 'MSXML2.XMLHTTP.4.0', 'MSXML2.XMLHTTP.3.0', 'MSXML2.XMLHTTP', 'Microsoft.XMLHTTP'];
            for (var n = 0; n < MSXML.length; n++) {
                try {
                    var objXMLHttp = new ActiveXObject(MSXML[n]);
                    break;
                }
                catch (e) {
                }
            }
        }
        // mozilla某些版本没有readyState属性
        if (objXMLHttp.readyState == null) {
            objXMLHttp.readyState = 0;
            objXMLHttp.addEventListener("load", function() {
                objXMLHttp.readyState = 4;
                if (typeof objXMLHttp.onreadystatechange == "function") {
                    objXMLHttp.onreadystatechange();
                }
            }, false);
        }
        return objXMLHttp;
    },
    // 发送请求(方法[post,get], 地址, 数据, 回调函数)
    sendReq: function(method, url, data, callback) {
        var objXMLHttp = this._getInstance();
        with (objXMLHttp) {
            try {
                // 加随机数防止缓存
                if (url.indexOf("?") > 0) {
                    url += "&randnum=" + Math.random();
                }
                else {
                    url += "?randnum=" + Math.random();
                }
                open(method, url, true);
                setrequestheader("cache-control", "no-cache"); //不缓存请求页面
                setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8'); // 设定请求编码方式
                send(data);
                onreadystatechange = function() {
                    if (objXMLHttp.readyState == 4 && (objXMLHttp.status == 200 || objXMLHttp.status == 304)) {
                        callback(objXMLHttp);
                        url = null;
                        data = null;
                        callback = null;
                        method = null;
                        CollectGarbage();
                    }
                }
            }
            catch (e) {
                alert("脚本出错:" + e);
            }
        }
    }
};

调用示例:

---

//发送信息
function sendMessage(username, uid, data1, user_to) {
    if (isNaN(uid)) return;
    var data = "[data]=" + escape(data1);
    var url = "Ajax_method.aspx?method=sendMessage&id=" + uid + "&username=" +escape(username) + "&user_to=" + user_to;
    XMLHttp.sendReq("post", url, data, function(request) {
        var state = request.responseText;
        if (state == "shibai") {
            alert("发送信息失败...");
        }
    });
}