SharePoint Lookup in other List (jQuery)

setSPLookup.js

// A $( document ).ready() block.
$( document ).ready(function() {
    console.log( "ready!" );
	
	var itemId = getUrlParameter("EventId");
    setLookupValue("Schulung_x002f_Unterweisung_6a5704d6-f2e4-46f4-9cf6-834e47e66d77_\\$LookupField", itemId);
	
    $("select[id=Schulung_x002f_Unterweisung_6a5704d6-f2e4-46f4-9cf6-834e47e66d77_\\$LookupField]").change(checkBooking);
    $("select[id=Schulung_x002f_Unterweisung_6a5704d6-f2e4-46f4-9cf6-834e47e66d77_\\$LookupField]").trigger( "change" );
})

function checkBooking ()
{
		_this = this;
  		var bookingcount = 0;
 		console.log ("Search for EventID:" + this.value);
  		//Query book Events  		
		$.ajax({
				cache: false,
				url: "/sites/a/departments/sav_biebesheim/schulungen/_api/web/lists/getByTitle('Schulung%20buchen')/items?$filter=(Schulung_x002f_Unterweisung eq " + this.value  + ")",
				type: 'GET',
				dataType: 'json',
				async: false,
				headers: {
				    "accept": "application/json;odata=verbose;charset=utf-8"
				}
				}).done(function(data) {
					console.log ("Booking Count:" + data.d.results.length);
					
					var selBookingsText = $(_this).find("option:selected").text();
					var selBookingsInt  = parseInt(selBookingsText.substring(selBookingsText.lastIndexOf (":")+1, selBookingsText.length).trim());
					console.log ("Seats:" + selBookingsInt);
					
					if (data.d.results.length >= selBookingsInt  )
					{
						reportStatus ('Diese Schulung ist bereits augebucht! Bitte wählen Sie eine andere Schulung aus.');
						$("input[value=Speichern]").prop("disabled",true);
					}
					else
					{
						reportStatus ('Diese Schulung ist verfügbar.');
						$("input[value=Speichern]").prop("disabled",false);
					}
		});				
}


function reportStatus (text) 
{
 	$(".reportmessage").remove();
	$(".ms-formtoolbar").before( "<b class='reportmessage'>" + text + "</b>" );
}



function renderAssignedTo(ctx) {
     //get current user properties
     var currentUser = $().SPServices.SPGetCurrentUser({fieldNames: ["Title", "Name"]});   //get current user properties
     var currentUserEntry = createUserEntity(currentUser.Name,currentUser.Title);

     //Set user default value
     ctx.CurrentFieldValue = [];   //Note: it is assumed the user field is aaa multi-valued field (!)
     ctx.CurrentFieldValue.push(currentUserEntry);  
     
     return SPClientPeoplePickerCSRTemplate(ctx);
}

function createUserEntity(userLoginName,userDisplayName)
{
   return {
      Description: userLoginName,
      DisplayText: userDisplayName,
      EntityGroupName: "",
      EntityType: "",
      HierarchyIdentifier: null,
      IsResolved: true,
      Key: userLoginName,
      MultipleMatches: [],
      ProviderDisplayName: "",
      ProviderName: ""
   };
}

function setLookupValue(fieldTitle, lookupVal)
{
    //Set default value for lookups with less that 20 items
    if ( $("select[id='" +fieldTitle+ "']").html() !== null)
    {
       $("select[id='"+ fieldTitle +"']").val(lookupVal);    
    }
    else
    {
        choices = $("input[id='" +fieldTitle +"']").attr("choices");
        hiddenInput = $("input[id='" +fieldTitle +"']").attr("optHid");
        $("input[id='" +hiddenInput +"']").attr("value",lookupVal)
        
        choiceArray = choices.split("|");
        for (index = 1; index < choiceArray.length; index = index + 2)
        {
            if (choiceArray[index] == lookupVal){
                $("input[id='" +fieldTitle +"']").val(choiceArray[index - 1]);    
            }
        }
    }
}

var getUrlParameter = function getUrlParameter(sParam) {
    var sPageURL = decodeURIComponent(window.location.search.substring(1)),
        sURLVariables = sPageURL.split('&'),
        sParameterName,
        i;

    for (i = 0; i < sURLVariables.length; i++) {
        sParameterName = sURLVariables[i].split('=');

        if (sParameterName[0] === sParam) {
            return sParameterName[1] === undefined ? true : sParameterName[1];
        }
    }
};