Question

it decorates objects, so I think it is, but I’m not sure.

example

jQuery(document).hide()

changes the document object by adding extra style.

EDIT:

If its not the Decorator Design Pattern? than what is it? There must be a pattern name for it!

Answer 1

jQuery best fits the facade pattern, as it does “define a higher-level interface that makes the subsystem easier to use.” For example, .css() and .hide() are features designed for ease of use, and so is jQuery’s ability to perform an action to multiple elements at once:

$('.foo').css({left: '100px', top: '100px'}).hide(); // jQuery

// Pure JavaScript
for(var a = document.getElementsByClassName('foo'), i = 0; i < a.length; ++i) {
    a[i].style.left = '100px';
    a[i].style.top = '100px';
    a[i].style.display = 'none';
}

jQuery only even seems to fit the decorator pattern in such ways as its animation functionality. Normal HTML DOM elements do not offer timed animations and attached queues, so jQuery adds that. In most other areas, jQuery provides the same functionality as available by accessing the underlying DOM elements directly.

But even there, it really doesn’t fit, as jQuery is not “dynamically keeping the same interface.”