implementation-identity.html - Android社区 - https://www.androidos.net.cn/

<body>
<script>
if (window.layoutTestController)
    layoutTestController.dumpAsText();

function print(message)
{
    var paragraph = document.createElement("li");
    paragraph.appendChild(document.createTextNode(message));
    document.getElementById("console").appendChild(paragraph);
}

function test()
{
    if (document.implementation != frames[0].document.implementation)
        print("OK: Top-level document and iframe document have different DOMImplementation objects");
    else
        print("BUG: Top-level document and iframe document share a DOMImplementation object");

    if (document.implementation === document.implementation)
        print("OK: DOMImplementation object is cached");
    else
        print("BUG: DOMImplementation object is not cached");
}
</script>
<p>This test checks that DOMImplementation object is created per document.</p>
<p>If the test passes, you should see a few OK lines below.</p>
<p><ol id=console></ol></p>
<iframe src="about:blank" onload="test()"></iframe>
</body>