CRM 2011 Retrieve values from other entity based on lookup value.

Retrieve product number based on product name entered in product lookup field

// JScript source code

productnumber = function () {
    if (Xrm.Page.getAttribute("productid").getValue() != null) {
        prdid = Xrm.Page.getAttribute("productid").getValue()[0].id;
        this.retrieveRecord(prdid, "Product", null, null, function (res) { this.successCallback(res) }, function () { alert(‘Error’); });              
    }
}

function successCallback(results) {
   debugger;
    var prdnumber = results.ProductNumber;
    var quan=results.QuantityOnHand;
    Xrm.Page.getAttribute("productnumber").setValue(prdnumber);
    Xrm.Page.getAttribute("availablequantity").setValue(quan);
}

retrieveRecord = function (id, type, select, expand, successCallback, errorCallback) {

    var systemQueryOptions = "";

    if (select != null || expand != null) {
        systemQueryOptions = "?";
        if (select != null) {
            var selectString = "$select=" + select;
            if (expand != null) {
                selectString = selectString + "," + expand;
            }
            systemQueryOptions = systemQueryOptions + selectString;
        }
        if (expand != null) {
            systemQueryOptions = systemQueryOptions + "&$expand=" + expand;
        }
    }
    var req = new XMLHttpRequest();
    var surl = Xrm.Page.context.getServerUrl();
    var url = http://localhost:5555/testing/XRMServices/2011/OrganizationData.svc/ + type + "Set(guid’" + id + "’)" + systemQueryOptions;
    req.open("GET", url, true);
    req.setRequestHeader("Accept", "application/json");
    req.setRequestHeader("Content-Type", "application/json; charset=utf-8");
    req.onreadystatechange = function () {
        if (this.readyState == 4 /* complete */) {
            if (this.status == 200) {
                successCallback(JSON.parse(this.responseText, this._dateReviver).d);
            }
            else {
                errorCallback(this._errorHandler(this));
            }
        }
    };
    req.send();
}

_dateReviver: function (key, value) {
    ///<summary>
    /// Private function to convert matching string values to Date objects.
    ///</summary>
    ///<param name="key" type="String">
    /// The key used to identify the object property
    ///</param>
    ///<param name="value" type="String">
    /// The string value representing a date
    ///</param>

    var a;
    if (typeof value === ‘string’) {
        a = /Date\(([-+]?\d+)\)/.exec(value);
        if (a) {
            return new Date(parseInt(value.replace("/Date(", "").replace(")/", ""), 10));
        }
    }
    return value;
}

function errorHandler(error) {
    writeMessage(error.message);
}