jQuery split into smaller files and load with ajax

gistfile1.js

function microAjax(url, callbackFunction) {
    this.bindFunction = function (caller, object) {
        return function() {
            return caller.apply(object, [object]);
        };
    };
    this.stateChange = function (object) {
        if (this.request.readyState==4)
            this.callbackFunction(this.request.responseText);
    };
    this.getRequest = function() {
        if (window.ActiveXObject)
            return new ActiveXObject('Microsoft.XMLHTTP');
        else if (window.XMLHttpRequest)
            return new XMLHttpRequest();
        return false;
    };
    this.postBody = (arguments[2] || "");
    this.callbackFunction=callbackFunction;
    this.url=url;
    this.request = this.getRequest();
    if (this.request) {
        var req = this.request;
        req.onreadystatechange = this.bindFunction(this.stateChange, this);
        if (this.postBody!=="") {
            req.open("POST", url, false);
            req.setRequestHeader('X-Requested-With', 'XMLHttpRequest');
            req.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
            req.setRequestHeader('Connection', 'close');
        } else {
            req.open("GET", url, false);
        }
        req.send(this.postBody);
    }
}

var jquerysource = '';
microAjax("/js/jquerypart1.txt", function (res) { jquerysource =res; });
microAjax("/js/jquerypart2.txt", function (res) { jquerysource+=res; });
eval(jquerysource);