jQuery add elements to empty selection?

Question

Why doesn\'t this work?

var spans = $();
var elem = document.getElementById(\'someId\');
spans.add(elem);

What is the proper way to start

Answer 1

There may be better ways to do what you're trying, but if you just want to create an empty jQuery object, use this:

var $foo = $([]);

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Edit: I should clarify - your code actually should work, unless you're using an older version of jQuery, in which case $() would create a collection containing the document object. In newer versions, however, there's nothing wrong with that. The code snippet I pasted above is just something that should work in older versions and newer versions of jQuery.

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Edit 2: In response to this portion of the question: "I want to loop through a collection of ids and find the element on the page and add it to the matched set", the following code might be useful:

var ids = ['foo', 'bar', 'baz'],
    selector = $.map(ids, function(i, id) {
        return '#' + id;
    }).join(','),
    $collection = $(selector);