How to serialize DOM node to JSON even if there are circular references?

Question

I want to serialize DOM node or even whole window to JSON.

For example:

 >> serialize(document)
    -> {
      "URL": "http://stackoverflow.com/posts/2303713",
      "body": {
        "aLink": "",
        "attributes": [
          "getNamedItem": "function getNamedItem() { [native code] }",
          ...
        ],
        ...
        "ownerDocument": "#" // recursive link here
      },
      ...
    }

JSON.stringify()

JSON.stringify(window) // TypeError: Converting circular structure to JSON

The problem is JSON does not support circular references by default.

var obj = {}
obj.me = obj
JSON.stringify(obj) // TypeError: Converting circular structure to JSON

window and DOM nodes have many of them. window === window.window as will as document.body.ownerDocument === document.

Also, JSON.stringify does not serialize functions, so this is not what I'm looking for.

dojox.json.ref

 `dojox.json.ref.toJson()` can easily serialize object with circular references:

    var obj = {}
    obj.me = obj
    dojox.json.ref.toJson(obj); // {"me":{"$ref":"#"}}

Good, isn't it?

 dojox.json.ref.toJson(window) // Error: Can't serialize DOM nodes

Well not good enough for me.

Why?

I'm trying to make DOM compatibility table for different browsers. For instance, Webkit supports placeholder attribute and Opera doesn't, IE 8 supports localStorage and IE 7 doesn't, and so on.

I don't want to make thousands of test-cases. I want to make generic way for test them all.

Update, June 2013

I made a prototype NV/dom-dom-dom.com.

Answer 1

http://jsonml.org/ takes a shot at a grammar for converting XHTML DOM elements into JSON. An an example:

<ul>
    <li style="color:red">First Item</li>
    <li title="Some hover text." style="color:green">Second Item</li>
    <li><span class="code-example-third">Third</span> Item</li>
</ul>

becomes

["ul",
    ["li", {"style": "color:red"}, "First Item"],
    ["li", {"title": "Some hover text.", "style": "color:green"}, "Second Item"],
    ["li", ["span", {"class": "code-example-third"}, "Third"], " Item" ]
]

Haven't used it yet, but thinking about using it for a project where I want to take any web page and re-template it using mustache.js.