postMessage test

HTML

<button>postMessage</button>
<iframe src="http://example.com" frameborder="0"></iframe>

JavaScript

$("button").on("click",function(){
      const iframe = document.getElementsByTagName('iframe')[0]
    window.addEventListener('message', console.log)
    iframe.contentWindow.addEventListener('message', console.log)
    setTimeout(() => {
      iframe.contentWindow.postMessage('aaaa', '*')
    }, 2000);
});