$("body").data("foo", 52);
　　$("body").data("bar", { myType: "test", count: 40 });
　　$("body").data({ baz: [ 1, 2, 3 ] });

　　$("body").data("foo"); // 52
　　$("body").data(); // { foo: 52, bar: { myType: "test", count: 40 }, baz: [ 1, 2, 3 ] }

 $(document).on('click.modal.data-api', '[daTa-toggle="modal"]', function (e) {
  alert($(this).data().toggle) //这行是我加入的代码 打印的值是modal
  var $this = $(this)
   , href = $this.attr('href')
   , $target = $($this.attr('data-target') || (href && href.replace(/.*(?=#[^\s]+$)/, ''))) //strip for ie7
   , option = $target.data('modal') ? 'toggle' : $.extend({ remote:!/#/.test(href) && href }, $target.data(), $this.data())  
  e.preventDefault()
  $target
   .modal(option)
   .one('hide', function () {
    $this.focus()
   })
 })

option = $.extend({ remote:!/#/.test(href) && href }, $target.data(), $this.data()) //结果是 option= {remote: false,toggle: "modal"}

    // Gets all values
    if ( key === undefined ) {
      if ( this.length ) {
        data = jQuery.data( elem );
        if ( elem.nodeType === 1 && !jQuery._data( elem, "parsedAttrs" ) ) {
          attrs = elem.attributes;
          for ( ; i < attrs.length; i++ ) {
            name = attrs[i].name;
            if ( name.indexOf("data-") === 0 ) {
              name = jQuery.camelCase( name.slice(5) );

              dataAttr( elem, name, data[ name ] );
            }
          }
          jQuery._data( elem, "parsedAttrs", true );
        }
      }
      return data;
    }

<div data-role="page" data-last-value="43" data-hidden="true" data-options='{"name":"John"}'></div>

$("div").data("role") === "page";
$("div").data("lastValue") === 43;
$("div").data("hidden") === true;
$("div").data("options").name === "John";