gtmnode.js

 tagmanager.accounts.containers.triggers.create(
        {     
            accountId : accountId,
            containerId : containerId,
            name : "First Trigger",
            type : "customEvent",
            eventName: {
                type: "template",
                value: "firstTrigger"
            }
            
        }, function(err){
            if (err) {
                res.json({error : err});
            }
            else {
                res.json({message : "success!"});
            }
        }