error starting sp2010 workflow in sharepoint Online using javascript

Question

I am trying to start a sharepoint 2010 style workflow which is configured on a list in sharepoint Online. I can't figure out where my problem is - each time I try to start the workflow with code, an error is thrown with the text "itemGuid" of type "System.ArgumentException"

The list is a survey, and I am unable to create sharepoint 2013 style workflows against it. I am able to manually start the workflow via the web browser.

code sample is below:

function testWorkflow_Start(){
    var myListName="MyTestListName";
    var myItemId=1226;
    var context = new SP.ClientContext.get_current();
    var list=context.get_web().get_lists().getByTitle(myListName);
    var item=list.getItemById(myItemId);
    context.load(list,'Id');
    context.load(item);
    context.executeQueryAsync(function(){
        console.log("item uniqueID:"+item.get_item("UniqueId"));
        console.log("listId:"+list.get_id());
        var wfServicesManager = new SP.WorkflowServices.WorkflowServicesManager(context, context.get_web());
        var interopService = wfServicesManager.getWorkflowInteropService()
        interopService.startWorkflow("SRDTest", null, list.get_id(), item.get_item("UniqueId"), null);        
        context.executeQueryAsync(function(){
            console.log("success");
        },
        function(sender,args){
            console.log("Error:"+args.get_message()); //returns: "itemGuid"
        });
    },function (sender,args){
        console.log("error occurred");
    });
}

I've also tried passing in the GUIDs as strings, but I get the same error.

I created a test list and test sp2010-style workflow in our sharepoint 2013 on-prem environment - it produced the same error. In that environment I was able to get the Correlation ID and track down the error in the ULS logs, but it isn't much help to me:

Original error: System.ArgumentException: itemGuid    
 at Microsoft.SharePoint.WorkflowServices.FabricInteropProvider.StartWorkflow(String associationName, Guid correlationId, Guid listId, Guid itemGuid, IDictionary`2 workflowParameters)    
 at Microsoft.SharePoint.WorkflowServices.WorkflowInteropServiceServerStub.StartWorkflow_MethodProxy(WorkflowInteropService target, XmlNodeList xmlargs, ProxyContext proxyContext)    
 at Microsoft.SharePoint.WorkflowServices.WorkflowInteropServiceServerStub.InvokeMethod(Object target, String methodName, XmlNodeList xmlargs, ProxyContext proxyContext, Boolean& isVoid)    
 at Microsoft.SharePoint.Client.ServerStub.InvokeMethodWithMonitoredScope(Object target, String methodName, XmlNodeList args, ProxyContext proxyContext, Boolean& isVoid)

The on-prem ULS Log also shows the request parameters for the CSOM call - which are below:

<Request xmlns="http://schemas.microsoft.com/sharepoint/clientquery/2009" SchemaVersion="15.0.0.0" LibraryVersion="15.0.0.0" ApplicationName="Javascript Library">
    <Actions>
        <ObjectPath Id="33" ObjectPathId="32" />
        <ObjectPath Id="35" ObjectPathId="34" />
        <Method Name="StartWorkflow" Id="36" ObjectPathId="34">
            <Parameters>
                <Parameter Type="String">wfStartTest</Parameter>
                <Parameter Type="Null" />
                <Parameter Type="Guid">{357abe32-faac-4b15-a4ed-a823272e7f66}</Parameter>
                <Parameter Type="Guid">{f3c8da6b-a2bd-48ee-b21e-78a0501cd7d5}</Parameter>
                <Parameter Type="Null" />
            </Parameters>
        </Method>
    </Actions>
    <ObjectPaths>
        <Constructor Id="32" TypeId="{4ccc7f0e-bf7e-4477-999c-6458a73d0039}">
            <Parameters>
                <Parameter ObjectPathId="18" />
            </Parameters>
        </Constructor>
        <Method Id="34" ParentId="32" Name="GetWorkflowInteropService" />
        <Property Id="18" ParentId="16" Name="Web" />
        <StaticProperty Id="16" TypeId="{3747adcd-a3c3-41b9-bfab-4a64dd2f1e0a}" Name="Current" />
    </ObjectPaths>
</Request>

Answer 1

Correct way to get list item Guid is:

item.get_item("GUID")