What's different between '.current' and 'current'?


#1

I saw two kinds of 'current' within this code.
One is with dot in front of 'current', one is not.
Could anyone kindly tell me what's the difference between them, and when I should use '.current' and 'current'.

        else if (event.which===110){
        var currentArticle=$('.current');
        var nextArticle=currentArticle.next();
        currentArticle.removeClass('current');
        nextArticle.addClass('current');

#2

+++++ addClass removeClass

Every HTML-Element has so called attributes.
One of the possible attributes, is the class-attribute.

If you write the HTML-document, you add the class-attribute
within the Element-Tag by using the syntax
class-keyword = then a string
containing the class-name
OR mutliple class-names which are =separated=from=eachother= by a space

Thus with

 <div class="myClass1 myClass2 myClass3" ></div>

you now have a DIV-Element carrying 3 classes myClass1, myClass2 and myClass3

As part of its CSS-category-of-Methods jQuery gives you the ability
to manipulate this class-attribute
by providing the addClass()-, removeClass()-, toggleClass()-Methods.
You will have to provide the Method at least 1 argument
which is the string VALUE of the class-name.
Thus you have to change
**$('.article').removeClass('.current')
$(this).addClass('.current')**
into
**$('.article').removeClass('current')
$(this).addClass('current')**

The confusion when to use a pre-pending dot or NOT...
In the Cascading Style Sheet syntax,
you have to prepend-a-dot to the classname
so the CSS will interpret it as a class-attribute
So in the file style.css you will find an object
identified by .current,
In this .current object
the background property-key is set to a particular VALUE

jQuery uses the same syntax to identify a class-attribute
like in the jQuery-selector
$(".current") by which this HTML-Element and all it's CHILDREN
are selected into a jQuery-object,

This parent-HTML-Element carries the class-attribute with class-name "current"

Reference::

google search
class site:jquery.com
https://api.jquery.com/category/selectors/
http://api.jquery.com/class-selector/
https://api.jquery.com/element-selector/
http://www.w3schools.com/jquery/jquery_ref_selectors.asp
http://www.w3schools.com/jquery/trysel.asp

what is CSS explained site:developer.mozilla.org
https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Getting_started/What_is_CSS

= http://stackoverflow.com/questions/1795438/load-and-execution-sequence-of-a-web-page