In the following example...

var options = {
                name: “activityName ",
                parameters: [{name: "param1", value: "Page1.prop1", isProperty: true},  {name: "param2", value: 123, isProperty: false}],
                contextPage: "page1.page2 ",
                event: eventObject
            };

            pega.api.ui.actions.runActivity(options);