Email Address should be unique in contact form by JS

Hi Everyone,

I Have Stuck in a Query. My requirement is simply that email address should be unique for a contact record. One record has a unique email address and if user creates another record with earlier existing email address, then form should not save and shows a alert message.

I can do this thing by plugin. But I want to do by JS. I have searched a lot on google and find odata JS Query, Xrm toolkit.

But unfortunately, My requirement is not fulfill. I have used below Odataquery code and read about a retrievemultiplerecords function in XrmServicetoolkit.

function Account_onchange() {
debugger;
alert("one");
//var accountId = Xrm.Page.getAttribute('parentcustomerid').getValue();

var accountId = Xrm.Page.getAttribute('emailaddress1'); 



alert("two");
    if (accountId != null) {
        var contacts = GetContactsByAccount(accountId);
        if (contacts != null && contacts[0].results.length > 0) {
            for (var count = 0; count < contacts[0].results.length; count++) {
alert("Rest");
                alert(contacts[0].results[count].ContactId);
                alert(contacts[0].results[count].LastName);
            }
        }
alert("There is no data");
}

}

function GetContactsByAccount(accountId) {

debugger;
   var serverUrl = "http://" + window.location.host + "/" + Xrm.Page.context.getOrgUniqueName();

    var oDataPath = serverUrl + "/XRMServices/2011/OrganizationData.svc";

var oDataUri = oDataPath + "/ContactSet?$select=ContactId,LastName&$filter=EMailAddress1 eq '" + 

accountId +"'";

    var jSonArray = new Array();

    jQuery.ajax({
        type: "GET",
        contentType: "application/json; charset=utf-8",
        datatype: "json",
        url: oDataUri,
        async: false,
        beforeSend: function (XMLHttpRequest) {
            //Specifying this header ensures that the results will be returned as JSON.            
            XMLHttpRequest.setRequestHeader("Accept", "application/json");
        },
        success: function (data, textStatus, XmlHttpRequest) {
            if (data && data.d != null) {
                jSonArray.push(data.d);
            }
        },
        error: function (XmlHttpRequest, textStatus, errorThrown) {
            alert("Error :  has occured during retrieval of the contacts");
        }
    });

    return jSonArray;
alert(jSonArray);
}

Please help on this.

I will appreciate your view.

Thanks in Advance

Vivek Gupta