JS: Basic pure js plugin structure

PluginStructure.js

(function () {
    // Define the constructor
    this.Modal = function () {
        // Create global element references
        this.closeButton = null;
        this.modal = null;
        this.overlay = null;


        // Define options defaults
        var defaults = {
            className: 'fade-and-drop',
            closeButton: true,
            content: '',
            maxWidth: 600,
            minWidth: 280,
            overlay: true
        };

        // Create options by extending defaults with the passed in arguments
        if (arguments[0] && typeof arguments[0] === "object") {
            this.options = extendDefaults(defaults, arguments[0]);
        }

        // Public methods
        Modal.prototype.open = function() {
            // Open code
        };

        // Private methods
        // Utility method to extend defaults with user options
        function extendDefaults (defaults, options) {
            var option;
            for (option in options) {
                if (options.hasOwnProperty(option)) {
                    defaults[option] = options[option];
                }
            }

            return defaults;
        }
    }
}());