JS类库——XMLHttpRequestPool

XMLHttpRequestPool.js

/* 建一个XMLHttpRequest对象池 */
/**
 * XMLHttpRequest Object Pool
 * @author    skey <skey_chen@163.com>
 */
var __XMLHttp__ = {
    _objPool: [],
    _getInstance:function() {
        for (var i = 0; i < this._objPool.length; i++) {
            // 判断是否有未使用或者请求已经完成的对象
            if (this._objPool[i].readyState == 0
                    || this._objPool[i].readyState == 4
                    || this._objPool[i].readyState == "complete") {
                return this._objPool[i];
            }
        }
        this._objPool[this._objPool.length] = this._createObj();// IE5中不支持push方法
        return this._objPool[this._objPool.length - 1];
    },
    _createObj:function() {
        if (window.XMLHttpRequest) {
            // mozilla版本
            var objXMLHttp = new XMLHttpRequest();
        }
        else {
            // windows版本,Microsoft.XMLHTTP为IE6.0以下版本
            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)
    // ajax众多的frame都有callback的function, 但参数是规定好的, 在framework的prototype中都定义了
    sendRequest: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);
                // 设定请求编码方式
                setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8');
                send(data);
                onreadystatechange = function() {
                    if ((objXMLHttp.readyState == 4 || objXMLHttp.readyState == "complete")
                        && (objXMLHttp.status == 200 || objXMLHttp.status == 304)) {
                        callback(objXMLHttp);// 相当于调用回调函数,并以objXMLHttp作为参数
                    }
                }
            }
            catch(e) {
                // alert(e);
            }
        }
    }
}
//__XMLHttp__.sendRequest('GET', urlPage, '', returnFunction);
//function returnFunction(obj){obj.responseText;obj.responseHTML;}

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