Postmessage from Node-Red to webpage

hi, i am trying to interact from Node-Red towards a webpage (online POS) via Postmessage.
already tried a lot of options but without succes. Hope someone can help me getting started.

Is there a node where i can pass this message to another open tab in the browser?

window.postMessage(JSON.stringify({
   method: 'add-customer',
   params: {
     customer_id: '080027ac-bd2c-11e5-ec95-d12579aa90a3'
   }
 }), window.location.origin);