.add() not working on cached jQuery object

[markahon]

Can't use $.fn.add to add more elements into a cached jQuery object containing DOM elements.

If this works as intended, then at least the documentation on  http://api.jquery.com/add/ is not clear about this, and then why shouldn't it be allowed?

I stumbled into this when I wanted to use .add() inside a loop to add an element into a collection, if certain criteria is fulfilled. The jQuery object containing the elements that fulfilled the criteria would be processed later.

Test code:

var d = $('div');
alert('divs: '+d.length);

// using add(), this failed
d = $();
$.each($('div'), function() {
  d.add(this);
});
alert('divs, using add() in a loop: '+d.length);

// workaround
d = [];
$.each($('div'), function() {
  d.push(this);
});
alert('divs, using array workaround: '+$(d).length);

[john]

.add() doesn't modify the existing object, it returns a new object with the values in it - it's more like using .concat() then .push.

[markahon]

Ah, thank you for the quick answer. This was revealing, before now it had somehow felt natural to assume that the existing object is modified when the traversing functions are used.