{
var channel = new MessageChannel();
var output = foo.querySelector('.output');
var iframe = foo.querySelector('iframe');
console.log(iframe)
iframe.addEventListener("load", onLoad);
function onLoad() {
console.log("onload called")
channel.port1.onmessage = onMessage;
iframe.contentWindow.postMessage('Hello from the main page!', '*', [channel.port2]);
}
function onMessage(e) {
output.innerHTML = e.data;
}
}