jsomwf.js

function LoadScripts(){
	SP.SOD.executeFunc("sp.js", "SP.ClientContext" , function(){
		SP.SOD.registerSod('sp.workflowservices.js', SP.Utilities.Utility.getLayoutsPageUrl('sp.workflowservices.js'));
		SP.SOD.executeFunc('sp.workflowservices.js', "SP.WorkflowServices.WorkflowServicesManager", StartSiteWorkflow);
	})    
}

function StartSiteWorkflow(){

	var context = SP.ClientContext.get_current();
			
	var web = context.get_web();
				
	//Workflow Services Manager
	var wfServicesManager = new SP.WorkflowServices.WorkflowServicesManager(context, web);
				
	//Workflow Interop Service used to interact with SharePoint 2010 Engine Workflows
	var interopService = wfServicesManager.getWorkflowInteropService()
				
	//Initiation Parameters have to be in a plain JS Object.
	var initiationParameters = {
		FirstName: "Vardhaman",
		LastName: "Deshpande"
	};
				
	//Start the Site Workflow by Passing the name of the Workflow and the initiation Parameters.
	interopService.startWorkflow("My Workflow", null, null, null, initiationParameters);

	context.executeQueryAsync(function () {
		console.log("workflow started");
	},
	function (sender, args) {
		console.log(args.get_message());
	});
}

jQuery(document).ready(function () {
	LoadScripts();
});