Communication between an iframe and its parent window

// Called from the iframe
window.parent.postMessage(message, '*');

// Called from the iframe
const message = JSON.stringify({
    message: 'Hello from iframe',
    date: Date.now(),
});
window.parent.postMessage(message, '*');

// Called from the page
frameEle.contentWindow.postMessage(message, '*');

window.addEventListener('message', function (e) {
    // Get the sent data
    const data = e.data;

    // If you encode the message in JSON before sending them,
    // then decode here
    // const decoded = JSON.parse(data);
});

// From a child iframe
const message = JSON.stringify({
  channel: 'FROM_FRAME_A',
  ...
});
window.parent.postMessage(message, '*');

window.addEventListener('message', function (e) {
    const data = JSON.parse(e.data);
    // Where does the message come from
    const channel = data.channel;
});