jQuery Countable Plugin

jquery.countable.js

;(function ( $, window, undefined ) {
  var pluginName = 'countable',
      document = window.document,
      defaults = {
        step: 1,
        min: 1,
        max: 0,
        value: 1,
        increase: ".increase",
        decrease: ".decrease",
        fn: function() {}
      };

  function Plugin( element, options ) {
    this.element = element;
    this.options = $.extend( {}, defaults, options) ;
    this._defaults = defaults;
    this._name = pluginName;
    this.init();
  }

  Plugin.prototype.init = function () {
    var that = this;

    this.changeValue();

    $(this.element).on("click", this.options.increase, function(e) {
      that.changeValue("increase");
      e.preventDefault();
    });
    $(this.element).on("click", this.options.decrease, function(e) {
      that.changeValue("decrease");
      e.preventDefault();
    });
  };
  Plugin.prototype.changeValue = function(type) {
    if (type == "increase") {
      if (this.options.max == 0 || this.options.value + this.options.step <= this.options.max) {
        this.options.value += this.options.step;
      }
    } 
    if (type == "decrease") {
      if (this.options.min == 0 || this.options.value - this.options.step >= this.options.min) {
        this.options.value -= this.options.step;
      }
    }
    this.options.fn.call(this);
  };

  $.fn[pluginName] = function ( options ) {
    return this.each(function () {
      if (!$.data(this, 'plugin_' + pluginName)) {
        $.data(this, 'plugin_' + pluginName, new Plugin( this, options ));
      }
    });
  }

}(jQuery, window));