When a <menu> element is shown as a context menu in HTML, the onshow event fires.
Example
You can try to run the following code to execute a script when a <menu> element is displayed as a context menu −
<!Doctype html>
<html>
<head>
<title>HTML menu</title>
</head>
<body>
<div style = "border:1px solid #000; padding:20px;" contextmenu = "clickmenu">
<p>Right click inside here....</p>
<menu type = "context" id = "clickmenu" onshow="display()">
<menuitem label = "Tutorialspoint" onclick = ""></menuitem>
<menuitem label = "Tutorials Library" onclick = ""></menuitem>
<menuitem label = "Coding Ground" onclick = ""></menuitem>
<menuitem label = "Q/A" onclick = ""></menuitem>
</menu>
</div>
<script>
function display() {
alert("The context menu will be visible now.");
}
</script>
</body>
</html>