HTML DOM Window top( ) Property

The Window top() property is used to return the topmost browser window of a current window. It is a read-only property and it returns a reference to the topmost window in the window hierarchy.
Syntax:

window.top

Return Value: It returns the reference of the topmost window in the window hierarchy.

Below program illustrates the Window top() property :
Checking whether the window is the topmost browser window or not.

html

<!DOCTYPE>
<html>
  
<head>
    <title>
      Window top() property in HTML
    </title>
    <style>
        h1 {
            color: green;
        }
          
        h2 {
            font-family: Impact;
        }
          
        body {
            text-align: center;
        }
    </style>
</head>
  
<body>
  
    <h1>GeeksforGeeks</h1>
    <h2>Window top() Property</h2>
  
      
  
<p>
      For checking whether the window is the 
      topmost window or not, double click the 
      "Check Top Window" button: 
    </p>
  
  
  
    <button ondblclick="Window()">
      Check Top Window
    </button>
  
    <p id="MyWindow"></p>
  
  
  
    <script>
        function Window() {
            if (window.top = window.self) {
                document.getElementById("MyWindow").innerHTML =
                    "This window is the topmost window.";
            } else {
                document.getElementById("demo").innerHTML =
                    "This window is not the topmost window.";
            }
        }
    </script>
</body>
  
</html>