Question

I am trying to understand some jquery code that uses a $(this) node. What is it used for and when can it be used?

$("li").hover(border, noBorder);
function border()
{
    $(this).css("border", "1px solid black");
}

Answer 1

Please read jQuery’s this:demystified by Remy Sharp

There are really two main contexts of
‘this’ in jQuery. The first refers to
a to a DOM element, and the second to
a jQuery object.

As a DOM Element

$('a.newTarget').each(function () { // <- our anonymous callback
    // check the DOM attribute 'host' on this
    if (this.host != window.location.host) {
        // create a jQuery object using the current DOM element
        $(this).attr('target', '_new');
    }
});

As a jQuery Object

jQuery.fn.newTarget = function () {
    // 'this' is a jQuery object at this point - with all the jQuery functions

    return this.each(function () { // return so we don't break the chain
        // now we are inside of a jQuery function, the DOM element is the context
        // so 'this' has changed to become a DOM element.

        if (this.host != window.location.host) {
            $(this).attr('target', '_new');
        }
    });
};

Hope this helps.