About the usage of jquery data() in treetable

About the usage of jquery data() in treetable


I recently try to read source codes in jquery treetable in deep, and found some problems I don't know.
here is the problem about the usage of jquery data, and the code snippet is following:
  1.  init: function(options, force) {
          var settings;

          settings = $.extend({
            branchAttr: "ttBranch",
            clickableNodeNames: false,
            column: 0,
            columnElType: "td", // i.e. 'td', 'th' or 'td,th'
            expandable: false,
            expanderTemplate: "<a href='#'>&nbsp;</a>",
            indent: 19,
            indenterTemplate: "<span class='indenter'></span>",
            initialState: "collapsed",
            nodeIdAttr: "ttId", // maps to data-tt-id
            parentIdAttr: "ttParentId", // maps to data-tt-parent-id
            stringExpand: "Expand",
            stringCollapse: "Collapse",

            // Events
            onInitialized: null,
            onNodeCollapse: null,
            onNodeExpand: null,
            onNodeInitialized: null
          }, options);

          return this.each(function() {
            var el = $(this), tree;

            if (force || el.data("treetable") === undefined) {
              tree = new Tree(this, settings);

              el.addClass("treetable").data("treetable", tree);

              if (settings.onInitialized != null) {

            return el;

the main problem is about el.addClass("treetable").data("treetable", tree);
why it can store the tree data via data("treetable", tree), and when I use chrome to debug
this code snippet, i didn't see any data-treetable attribute in "this" instruction content, even
to tree data.
And then what's more, when I click and invoke function node, the code snippet as below
  1.  node: function(id) {
          return this.data("treetable").tree[id];

it really get the data from this.data("treetable").tree[id], but still I can not find any info about that
from chrome debug tools.  Is anyone know the reason and how it did , and what's its principle?