SharePoint JavaScript API for Workflow throws an error

Question

I am trying to access information about running workflows in a SharePoint list but I am running into problems with the workflow services JSOM library. I am using the workflow services just like every example I can find, see code below:

var context = SP.ClientContext.get_current();
var web = context.get_web();
var servicesManager = SP.WorkflowServices.WorkflowServicesManager.newObject(context, web);
var instanceService = servicesManager.getWorkflowInstanceService();

While executing the code, the last line in the above snippet throws an exception

TypeError: this.get_context is not a function.

Answer 1

Propbaly this error occurs since one of the specified files from SharePoint JavaScript library has not been loaded.

• SP.js
• SP.Runtime.js
• SP.WorkflowServices.js

To ensure that the specified file(s) has been loaded you could consider the following approach:

SP.SOD.registerSod('SP.ClientContext', SP.Utilities.Utility.getLayoutsPageUrl('sp.js'));
SP.SOD.registerSod('SP.WorkflowServices.WorkflowServicesManager', SP.Utilities.Utility.getLayoutsPageUrl('SP.WorkflowServices.js'));
SP.SOD.loadMultiple(['SP.ClientContext', 'SP.WorkflowServices.WorkflowServicesManager'], function(){

    var ctx = SP.ClientContext.get_current();
    var workflowServicesManager = SP.WorkflowServices.WorkflowServicesManager.newObject(ctx, ctx.get_web()); 
    var workflowSubscriptionService = workflowServicesManager.getWorkflowSubscriptionService();                
    //...    

});

SP.SOD.loadMultiple function is intended for loading on demand scripts which in turn is a part of SharePoint JavaScript Library. Alternatively you could utilize jQuery.getScript() from jQuery library.

Answer 2

@VadimGremyachev, I tried using your code example and I then got a TypeError related to SP.Utilities. I guess SP.Utilities is part of sp.js so it couldn't be used to load itself. The only way in which I was able to get it working correctly was to use both the SOD and ExecuteOrDelayUntilScriptLoaded methods. I don't know if this is a nuance of using this using client-side rendering to override a list view or just bad timing of script loading. The code that works is as follows:

ExecuteOrDelayUntilScriptLoaded(function () {
    ExecuteOrDelayUntilScriptLoaded(function () {
        SP.SOD.registerSod('SP.ClientContext', SP.Utilities.Utility.getLayoutsPageUrl('sp.js'));
        SP.SOD.registerSod('SP.WorkflowServices.WorkflowServicesManager', SP.Utilities.Utility.getLayoutsPageUrl('SP.WorkflowServices.js'));
        SP.SOD.loadMultiple(['SP.ClientContext', 'SP.WorkflowServices.WorkflowServicesManager'], function () {
            var context = SP.ClientContext.get_current();
            var web = context.get_web();
            var servicesManager = SP.WorkflowServices.WorkflowServicesManager.newObject(context, web);
            var instanceService = servicesManager.getWorkflowInstanceService();
        });
    }, "sp.js");
}, "sp.runtime.js");`