写AJAX的onreadystatechange Handle遇到的问题

function processReqChange() {
    // only if req shows "loaded"
    if (req.readyState == 4) {
        // only if "OK"
        if (req.status == 200) {
            // ...processing statements go here...
        } else {
            alert("There was a problem retrieving the XML data:\n" +
                req.statusText);
        }
    }
}

这里 req 对象必须是一个全局对象，我自己写了一个lib， 直接用 var wajax = new WebAJAX(); 方法获取一个实例，其中 wajax.core 为 req 对象，因为可能同时产生多个WebAJAX对象，所以不能用同一个processReqChange作为handle，请问如何既不用不重复写handle方法也能同时调用多个handle呢？

目前唯一的方法是

/* 执行请求  */
WebAJAX.prototype.doQuery1 = function() {
	try {
		var ajaxReq = this.core;
		// this.core.onreadystatechange = this.reqFunc;

		this.core.onreadystatechange = function () {
			var r = false;
			// only if req shows "loaded"
			if (ajaxReq.readyState == 4) {
				// only if "OK"
				if (ajaxReq.status == 200) {
					r = true;
					// ...processing statements go here...
				} else {
				//    alert("There was a problem retrieving the XML data:\n" +
				//        req.statusText);
				}
			}

			alert("readAJAXResult = " + r);
		}
		
		this.core.open(this.reqType, this.reqURL, true);
		this.core.send();
	} catch (e) {
		WebUtil.debug("do query failed ...");
	}
}

WebAJAX.prototype.doQuery2 = function() { ...

像这样先定义多个请求方法，然后new出来的对象调不同的方法

已自行解决，用eval

/* 设置提交方法 */
WebAJAX.prototype.setReqFunc = function(oFunc) {
	var _oFunc = "funcWebAJAX = " + "function(){}";
	if(typeof oFunc == "undefined" || null == oFunc) 
		_oFunc = "funcWebAJAX = " + "function(){}";
	else if(typeof oFunc == "function") 
		_oFunc = "funcWebAJAX = " + oFunc.toString();
	else if(typeof oFunc == "string") 
		_oFunc = oFunc;

	this.reqFunc = _oFunc;
}

/* 执行请求  */
WebAJAX.prototype.doQuery = function() {
	try {
		var wajaxCore = this.core;
		this.core.onreadystatechange = eval(this.reqFunc);
		this.core.open(this.reqType, this.reqURL, true);
		this.core.send();
	} catch (e) {
		WebUtil.debug("do query failed ...");
	}
}

function handle1() {
   ...........................
}

function handle2() {
   ...........................
}

var arrWajax = new Array();

arrWajax[1] = new WebAJAX(url1, handle1);
arrWajax[2] = new WebAJAX(url2, handle2);

.......

arrWajax[1].doQuery();
......
arrWajax[2].doQuery();
......

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