Implementing Accordion accordion custom plug-in based on jQuery

(function ($) {
  'use strict';
  var defaults = {
    url: null,
    param: {},
    data: {},
    fill: true,
    level_space: 15,
    onitemclick: null,
    style: {
      header: "accordion-header",
      header_title: "accordion-header-title",
      content: "accordion-content",
      selected: "selected",
      icon_base: "fa",
      icon_collapse: "fa-angle-up",
      icon_expand: "fa-angle-down"
    }
  }
  var methods = {
    init: function (options) {
      return this.each(function () {
        var $this = $(this);
        if (!$this.hasClass("accordion")) {
          $this.addClass("accordion");
        }
        var settings = $this.data('tw.accordion');
        if (typeof (settings) == 'undefined') {
          settings = $.extend({}, defaults, options);
          $this.data('tw.accordion', settings);
        } else {
          settings = $.extend({}, settings, options);
          $this.data('tw.accordion', settings);
        }
        if (settings.url) {
          $.ajax({
            type: "post",
            async: false,
            url: settings.url,
            data: settings.param,
            success: function (data) {
              settings.data = data;
            }
          });
        }
        if (settings.fill) {
          $this.height("100%");
        }
        if (settings.data.length > 0) {
          $this.data("count", settings.data.length);
          $.each(settings.data, function () {
            this.level = 1;
            var item = $this.accordion("add", this);
            $this.append(item);
          });
          if ($this.find("." + settings.style.selected).length == 0) {
            var data = $this.find(">li:first-child").data("data");
            $this.accordion("select", data);
          }
        }
      });
    },
    add: function (data) {
      var $this = $(this);
      var settings = $this.data("tw.accordion");
      var item = $("<li class=&#39;" + settings.style.header + "&#39;></li>");
      item.data("data", data);
      var header = $("<div class=&#39;" + settings.style.header_title + "&#39; data-accordion=&#39;" + data.id + "&#39;>" +
        "<i class=&#39;" + settings.style.icon_base + "" + data.icon + "&#39;></i>" +
        "<span>" + data.name + "</span></div>");
      header.css("padding-left", settings.level_space * data.level);
      item.append(header);
      if (data.childrens) {
        var toggle = $("<i class=&#39;" + settings.style.icon_base + "" + settings.style.icon_collapse + "&#39;></i>");
        toggle.css({ "font-size": "1.4em", "position": "absolute", "top": "7px", "right": "7px" });
        header.append(toggle);
        var content = $("<ul class=&#39;" + settings.style.content + "&#39;></ul>");
        content.data("count", data.childrens.length);
        $.each(data.childrens, function () {
          this.level = data.level + 1;
          var child = $this.accordion("add", this);
          content.append(child);
        });
        item.append(content);
      }
      header.click(function () {
        $this.accordion("select", data);
      });
      if (data.selected) {
        $this.accordion("select", data);
      }
      return item;
    },
    select: function (data) {
      var $this = $(this);
      var settings = $this.data("tw.accordion");
      var header = $this.find("[data-accordion=&#39;" + data.id + "&#39;]");
      var item = header.parent();
      if (!header.hasClass(settings.style.selected) && !item.hasClass(settings.style.selected)) {
        var sibling = item.siblings();
        sibling.removeClass(settings.style.selected).children("." + settings.style.selected).removeClass(settings.style.selected);
        sibling.children("." + settings.style.icon_expand).removeClass(settings.style.icon_expand).addClass(settings.style.icon_collapse);
        if (data.childrens) {
          item.addClass(settings.style.selected);
          header.find("." + settings.style.icon_collapse).removeClass(settings.style.icon_collapse).addClass(settings.style.icon_expand);
          if (settings.fill) {
            var count = item.parent().data("count") - 1;
            item.css("height", "calc(100% - " + (item.height() * count) + "px)");
          }
        } else {
          header.addClass(settings.style.selected);
        }
      }
      if (settings.onitemclick) {
        settings.onitemclick(data);
      }
    },
    update: function (url, param) {
      var $this = $(this);
      var settings = $this.data("tw.accordion");
      if (typeof url == "object") {
        settings.param = url;
      } else {
        settings.url = url;
        settings.param = param;
      }
      $this.accordion("init", settings);
    },
    destroy: function (options) {
      return $(this).each(function () {
        var $this = $(this);
        $this.removeData(&#39;accordion&#39;);
      });
    }
  }
  $.fn.accordion = function () {
    var method = arguments[0];
    var args = arguments;
    if (typeof (method) == &#39;object&#39; || !method) {
      method = methods.init;
    } else if (methods[method]) {
      method = methods[method];
      args = $.makeArray(arguments).slice(1);
    } else {
      $.error(&#39;Method &#39; + method + &#39; does not exist on tw.accordion&#39;);
      return this;
    }
    return method.apply(this, args);
  }
})(jQuery);

.accordion {
  margin:0;
  padding:0;
  font-size:14px;
}
  .accordion > .accordion-header {
    list-style: none;
    margin: 0;
    padding: 0;
    border-bottom: 1px solid #ddd;
  }
    .accordion > .accordion-header.selected > .accordion-header-title {
      color: #0094ff;
    }
    .accordion > .accordion-header > .accordion-header-title {
      position: relative;
      width: 100%;
      height: 35px;
      line-height: 35px;
      background: #eee;
      border-bottom: 1px solid #ccc;
      cursor: pointer;
    }
      .accordion > .accordion-header > .accordion-header-title > i:first-child {
        font-size: 1.3em;
      }
      .accordion > .accordion-header > .accordion-header-title > span {
        position: relative;
        top: -1px;
        left: 5px;
      }
    .accordion > .accordion-header > .accordion-content {
      display: none;
      width: 100%;
      height: calc(100% - 35px);
      margin: 0;
      padding: 0;
    }
    .accordion > .accordion-header.selected > .accordion-content {
      display: block;
    }
.accordion-content > .accordion-header {
    list-style: none;
    margin: 0;
    padding: 0;
}
  .accordion-content > .accordion-header.selected {
    color: #0094ff;
  }
  .accordion-content > .accordion-header > .accordion-header-title {
    position: relative;
    width: 100%;
    height: 32px;
    line-height: 32px;
    cursor: pointer;
    border-bottom: 1px solid #ccc;
  }
    .accordion-content > .accordion-header > .accordion-header-title:hover {
      background:#eee;
    }
    .accordion-content > .accordion-header > .accordion-header-title.selected {
      color: #fff;
      background: #0094ff;
      border-left: 3px solid #ff6a00;
      border-bottom: 0px;
    }
      .accordion-content > .accordion-header > .accordion-header-title > i:first-child {
        font-size: 1.2em;
      }
      .accordion-content > .accordion-header > .accordion-header-title > span {
        position: relative;
        top: -1px;
        left: 5px;
      }
      .accordion-content > .accordion-header > .accordion-header-title.selected > i:first-child {
        position:relative;
        left:-3px;
      }
      .accordion-content > .accordion-header > .accordion-header-title.selected > span {
        position: relative;
        top: -1px;
        left: 2px;
      }
    .accordion-content > .accordion-header > .accordion-content {
      display: none;
      width: 100%;
      height: calc(100% - 32px);
      margin: 0;
      padding: 0;
    }
    .accordion-content > .accordion-header.selected > .accordion-content {
      display: block;
    }