Query Data using the Web API

In the below function RetrieveParentAccount() i want to  show how to retrieve string, option Set, lookup and  to Two Option fields
I have test the   RetrieveParentAccount() function on form OnLoad of contact entity.

  function RetrieveParentAccount() {
   
    var accountLookup = Xrm.Page.getAttribute("parentcustomerid");
    if (accountLookup != null) {
        var accountLookupValue = accountLookup.getValue();
        var accountGuid = accountLookupValue[0].id;
        accountGuid = accountGuid.replace("{", "");
        accountGuid = accountGuid.replace("}", "");

        //name : is single line of text field
        //primarycontactid : is Lookup field
        //preferredcontactmethodcode: is optionset field
        //donotemail : is two option field

        //filter by lookup field
        // var filter = "&$filter=_primarycontactid_value eq 0F7AFC02-891C-E611-80E1-5065F38B0371";

        //filter byOptionset field
        //var filter = "&$filter=preferredcontactmethodcode eq 2";

        //filter TwoOption field
        var filter = "&$filter=donotemail eq false";
        var orderBy = "&$orderby=name asc";
        var expand = "&$expand=incident_customer_accounts($select=title)";

        //var query = "accounts?$select=name,_primarycontactid_value,preferredcontactmethodcode,donotemail" + filter + orderBy + expand ;

        var query = "accounts(" + accountGuid + ")?$select=name,_primarycontactid_value,preferredcontactmethodcode,donotemail" + expand;
        var webapiPath = Xrm.Page.context.getClientUrl() + "/api/data/v8.0/" + query;

        var service = new XMLHttpRequest();
        service.open("GET", webapiPath, false);
        service.setRequestHeader("Accept", "application/json");
        service.setRequestHeader("Content-Type", "application/json; charset=utf-8");
        service.setRequestHeader("OData-MaxVersion", "4.0");
        service.setRequestHeader("OData-Version", "4.0");
        service.setRequestHeader("Prefer", "odata.include-annotations=*"); 
        //service.setRequestHeader("Prefer", "odata.maxpagesize = 3"); this tag isused to retrieve no of records
        service.send();

        if (service.readyState == 4 /* complete */) {

            if (service.status == 201 || service.status == 200) {

                var result = eval('(' + service.responseText + ')');
                var name = result.name; // extract single line of text field
                var lookupGuid = result._primarycontactid_value; // extract Look up guid
                var lookupEntityName = result['_primarycontactid_value@Microsoft.Dynamics.CRM.lookuplogicalname']; //extract look up logical name
                var lookupName = result['_primarycontactid_value@OData.Community.Display.V1.FormattedValue']; // extract lookup text
                var booleanFieldValue = result.donotemail; // boolean field
                var booleanFieldText = result['donotemail@OData.Community.Display.V1.FormattedValue']; // boolean field text
                var optionsetValue = result.preferredcontactmethodcode; // extract optionSetValue
                var optionsetText = result['preferredcontactmethodcode@OData.Community.Display.V1.FormattedValue'];//extract optionset text
                var releatedEntityCaseTitle = result.incident_customer_accounts[0].title;
            }
        }
    }
}