On 9/07/11 1:12 AM, Ryosuke Niwa wrote:
On Fri, Jul 8, 2011 at 5:21 AM, Sean Hogan <shogu...@westnet.com.au <mailto:shogu...@westnet.com.au>> wrote:

    - MathJax (http://mathjax.org) is a JS lib that facilitates
    putting math onto the web by converting LaTeX or MathML markup in
    a page to HTML. By default MathJax triggers off the onload event
    to run this conversion on the page. When content containing math
    is dynamically added to the page, MathJax must be called manually
    to convert the new content. A DOM insertion listener could
    potentially be used to handle this conversion automatically.

    - A similar use-case is element augmentation too complex for CSS
    :before and :after

    - ARIA support in JS libs currently involves updating
    aria-attributes to be appropriate to behavior the lib is
    implementing. Attribute mutation listeners would allow an inverse
    approach - behaviors being triggered off changes to aria-attributes.

    - DOM insertion and removal listeners could facilitate the
    implementation of automatically updating Table-of-* (Headings /
    Images / etc).

It seems like all 3 use cases here can be implemented by observers that are called AFTER the fact, and do not requiere any events or callbacks before mutation.

I agree, but it's just a list of the top of my head - I was merely trying to assist with the request for use-cases.

An obvious advantage of callbacks that occur BEFORE mutation is that they can be used to implement post-mutation notifications. The reverse is impossible.

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