It seems like it would be handy to include an example of going between JQuery's .live() and YUI3's node-event-delegate. I'd do it myself, but don't feel like I understand either one well enough to give a definitive example.

The YUI3 equivalents are .getComputedStyle('width') and .getComputedStyle('height').

From the actual example:

// jQuery

$('.foo').each(
  function() {
    this.some_method();
  }
);

// YUI

Y.all('.foo').each(
  function() {
    this.some_method();
  }
);

Should be:

$('.foo').each(
  function() {
    $(this).some_method(); // notice the wrapped `this`
  }
);

While this in the traverser in YUI is a Node object, in jQuery is the actual HTMLElement! Not only the example should be edited, but a little note IMO is required.

YUI has a less cumbersome map feature than the example, that isn't restricted to nodes:

// Convert an array of numbers into an array of strings.
Y.Array.map([1, 2, 3, 4], function (item) {
  return '' + item;
});
// => ['1', '2', '3', '4']

So in the context of the example given, this could be a one-liner:

Y.Array.map(Y.all('a').getDOMNodes(), some_function);

I justs wanted to contribute that jQuery's ".is()" is the same as YUI's ".test()"

jQuery: Description: Get the immediately following sibling of each element in the set of matched elements. If a selector is provided, it retrieves the next sibling only if it matches that selector.

YUI: Returns the next matching sibling. Returns the nearest element node sibling if no method provided.

The two next() method will return different node if given selector matches siblings but not the cloest next node.

$.is == Y.test

In this statement, under the Events section, .bind() should be replaced with .on():

//Alternatively, you can use the bind() method
$('#foo').bind('click', fn);

For reference:
http://api.jquery.com/bind/

As of jQuery 1.7, the .on() method is the preferred method for attaching event handlers to a document.

.offset() in jQuery (as of 1.8.3) does not return the size of the node

I love the idea of this project, but there's a few other libraries out there that'd benefit from this style of comparison - Dojo, MooTools, Prototype and such.

So I'm asking this (an issue seemed to be the easiest way): Would a pull request with that sort of work be accepted?

I know it's jquery-yui3-rosetta-stone, but given that it's hosted under the more neutral jsrosettastone.com, I'm hopeful. Thanks. :)

Add examples on how to remove elements from DOM?

Could you add the translation for checking an object, took me a while to track down and is a useful function.

jQuery
$.isEmptyObject(object)

YUI
Y.Object.isEmpty(object)

thanks

Is the YUI equivilent to .attr() getAttr() or getAttrs? Not sure if it's a typo or I am missing something in my setup.
Thanks.

$.inArray(value, array)

is equivalent to

Y.Array.indexOf(array, value)

NOT

Y.Array.indexOf(value, array)

source: http://yuilibrary.com/yui/docs/api/classes/Array.html#method_indexOf

Might be useful to cover these differences

in JQuery its node.clone(withDataAndEvents ) //deep clone is mandatory, data and events optional
in YUI it is node.cloneNode(deep) //deep clone optional but deep includes subtree and attributes

Should cover event triggering/firing/simulating whatever, for native and custom events.

For instance http://jsfiddle.net/balupton/862Lg/ and http://jsfiddle.net/balupton/tFbum/ do not work together.

I just wanted to contribute this to the list. That jQuery's "is" is the same as YUI "test"

YUI 3.3 added the Array 1.5 methods to NodeList, such as concat. This should probably be mentioned.
Also I think you should probably recommend using Y.NodeList.getDomNodes instead of the private ._nodes property, but that is just my personal opinion...

Just wanted to suggest adding jQuery's .is( selector ) matches the YUI's .test( selector ).