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<html><body><h1>The Window Object</h1><h2>The opener Property</h2><p id="demo">Click the button to open a new window that writes "HELLO!" in the opener window.</p><button onclick="myFunction()">Try it</button><script>function myFunction() { const myWindow = window.open("", "", "width=300,height=300"); myWindow.opener.document.getElementById("demo").innerHTML = "HELLO!";}</script></body></html>