A basic jQuery plugin

HTML

<div>
    just a div.
</div>

<p>
    a paragraph.
</p>

JavaScript

(function($){
    $.fn.addBorder = function(color){
        this.css("border", "1px solid " + color);
        return this;
    }
    
    $.fn.applyCss = function(cssObject){
        this.css(cssObject);
        return this;
    }
}(jQuery));

$("div").addBorder("orange");

$("p").applyCss(
    {
        "background-color": "green", 
        "border": "1px dotted red"    
    }
).html("some new content.");