Question

I’m trying to store a reference of an HTML tag for later reuse.

e.g. If I click on a div and save a pointer to that div within Javascript, will there be a way I could serialize such pointer? So I could de-serialize it and use the pointer in another instance of the web application?

---

Only methods I can think of are the following:

• Use id or name attributes

• Create a CSS selector for that element

Any other ideas guys? =)

Answer 1

You could try generating an XPath string for the element – the more complex the string, the more accurate and portable an identifier it will be.

For example, a simple element-only XPath query string would not be very unique, and likely to re-occur:

'//html/body/div/div/p/strong'

Factoring in all attributes might be overkill

'//html/body[@onclick="somereallylongjavascript" and class="nosidebar"]/div[@id="wrapper" and @class="posts"]/div[@class="entry" and @id="firstentry"]/p[@class="first"]/strong'

But you could probably find a nice middle-ground by limiting to certain attributes, maybe just to IDs:

'//html/body/div[@id="wrapper"]/div[@id="firstentry"]/p/strong'

---

You can retrieve XPath natively in all browsers. There's the W3C method:

var myElement=document.evaluate(
  XPathstring,
  document,
  function(ns){return{'html':'http://www.w3.org/1999/xhtml','':null}[ns];},
  9,
  null
).singleNodeValue;

(the ns function is purely if you need application/xhtml+xml support)

The IE method is more simplistic but less flexible:

var myElement=document.selectSingleNode(XPathString);

---

Creating the XPath string is a different issue of course - there are various options, none native unfortunately. XPather is a moz add-on that provides an interface that does this - its source is MPL-ed and relatively simple but is probably more than you need. There are various shorter scripts available that provide simpler solutions.

Edit: Justin Johnson has provided a link to an SO answer containing a VERY short XPath-generating function. It's a bit simplistic, it uses odd id notation (id(blah) instead of [@id="blah"]) and doesn't toLowerCase() its tagNames which could impair portability, but other than that it looks perfect for your needs.