jQuery: plugin pattern

jquery.plugin_pattern.js

/*
 *  Project:
 *  Description:
 *  Author:
 *  License:
 */

// the semi-colon before function invocation is a safety net against concatenated
// scripts and/or other plugins which may not be closed properly.
;(function ( $, window, document, undefined ) {

    // undefined is used here as the undefined global variable in ECMAScript 3 is
    // mutable (ie. it can be changed by someone else). undefined isn't really being
    // passed in so we can ensure the value of it is truly undefined. In ES5, undefined
    // can no longer be modified.

    // window is passed through as local variable rather than global
    // as this (slightly) quickens the resolution process and can be more efficiently
    // minified (especially when both are regularly referenced in your plugin).

    var pluginName = "linkColor",
    // the name of using in .data()
        dataPlugin = "plugin_" + pluginName,
    // default options
        defaults = {
            color: "black"
        };

    var privateMethod = function () {
        console.log("private method");
    };

    // The actual plugin constructor
    var Plugin = function ( element ) {
        /*
         * Plugin instantiation
         */
        this.options = $.extend( {}, defaults );
    };

    Plugin.prototype = {

        init: function ( options ) {

            // extend options ( http://api.jquery.com/jQuery.extend/ )
            $.extend( this.options, options );

            /*
             * Place initialization logic here
             */
            this.element.css( 'color', 'red' );
        },

        destroy: function () {
            // unset Plugin data instance
            this.element.data( dataPlugin, null );
        },

        // public get method
        href: function () {
            return this.element.attr( 'href' );
        },

        // public chaining method
        changeBG: function ( color = null ) {
            color = color || this.options['color'];
            return this.element.each(function () {
                // .css() doesn't need .each(), here just for example
                $(this).css( 'background', color );
            });
        }
    }

    /*
     * Plugin wrapper, preventing against multiple instantiations and
     * allowing any public function to be called via the jQuery plugin,
     * e.g. $(element).pluginName('functionName', arg1, arg2, ...)
     */
    $.fn[ pluginName ] = function ( arg ) {

        var args, instance;

        // only allow the plugin to be instantiated once
        if (!( this.data( dataPlugin ) instanceof Plugin )) {

            // if no instance, create one
            this.data( dataPlugin, new Plugin( this ) );
        }

        instance = this.data( dataPlugin );

        instance.element = this;

        // Is the first parameter an object (arg), or was omitted,
        // call Plugin.init( arg )
        if (typeof arg === 'undefined' || typeof arg === 'object') {

            if ( typeof instance['init'] === 'function' ) {
                instance.init( arg );
            }

        // checks that the requested public method exists
        } else if ( typeof arg === 'string' && typeof instance[arg] === 'function' ) {

            // copy arguments & remove function name
            args = Array.prototype.slice.call( arguments, 1 );

            // call the method
            return instance[arg].apply( instance, args );

        } else {

            $.error('Method ' + arg + ' does not exist on jQuery.' + pluginName);

        }
    };

}(jQuery, window, document));