Error OnClick Javascript object is not defined

I believe in the last line you should replace the line

result = sforce.connection.update(updateRecords);

with result = sforce.connection.update(updatedRecords);

When you update record with Ajax Toolkit then the returned result is an JS object like this result{id:'001i000001d89wbAAA', success:'true', }in case success. You get the Id of the record updated. If you want to get the field value you have to Query again with this returned Id. The method is like thissObject[] result = connection.retrieve(string fieldList, string sObjectType, ID ids[]);

Here is an example. I am first creating a Account record with myName and then updating it with a phone no. To get the updated phone no, I have retrieved the Account with the returned Id. Then you can get the phone no like this qRresult[0].Phone. Hope this helps.

<apex:page showHeader="true" sidebar="true">
    <script type="text/javascript">
        var __sfdcSessionId = '{!GETSESSIONID()}';
    </script>
    <script src="../../soap/ajax/34.0/connection.js" type="text/javascript"></script>
    <script type="text/javascript">
        //create an account
        var account = new sforce.SObject("Account");
        account.Name = "myName";
        result = sforce.connection.create([account]);

        //update that account
        account.id = result[0].id;
        account.Phone = "1234567890";
        result = sforce.connection.update([account]);
        console.log("result" +result);
        var qRresult;
        if (result[0].getBoolean("success")) {
          console.log("account with id " + result[0].id + " updated");
          qRresult = sforce.connection.retrieve("Name,Phone", "Account", [result[0].id]);
          console.log("result" +qRresult);
          console.log("result" +qRresult[0].Phone);
        } else {
          console.log("failed to update account " + result[0]);
        }   
    </script>

</apex:page>