jQuery.expando = "jQuery" + ( version + Math.random() ).replace( /\D/g, "" )

"jQuery" + ".." + . == "jQuery..." 

jQuery30009423638425146147"

jQuery 300 024727210109188635 1
jQuery 300 024727210109188635 2

var acceptData = function( owner ) {
  // Accepts only:
  // - Node
  //  - Node.ELEMENT_NODE
  //  - Node.DOCUMENT_NODE
  // - Object
  //  - Any
  /* jshint -W018 */
  return owner.nodeType === 1 || owner.nodeType === 9 || !( +owner.nodeType );
};

// If it is a node unlikely to be stringify-ed or looped over
// use plain assignment
if ( owner.nodeType ) {
  owner[ this.expando ] = value;
// Otherwise secure it in a non-enumerable property
// configurable must be true to allow the property to be
// deleted when data is removed
} else {
  Object.defineProperty( owner, this.expando, {
    value: value,
    configurable: true
  } );
}

elem['jQuery3000247272101091886351'] = dataObj;
var person = {name: 'John', age: 30};
Object.defineProperty( person, 'jQuery3000247272101091886351', {
  value: dataObj,
  configurable: true
} );

cache: function( owner ) {
  // Check if the owner object already has a cache
  var value = owner[ this.expando ];
  // If not, create one
  if ( !value ) {
    value = {};
    // We can accept data for non-element nodes in modern browsers,
    // but we should not, see #8335.
    // Always return an empty object.
    if ( acceptData( owner ) ) {
      // If it is a node unlikely to be stringify-ed or looped over
      // use plain assignment
      if ( owner.nodeType ) {
        owner[ this.expando ] = value;
      // Otherwise secure it in a non-enumerable property
      // configurable must be true to allow the property to be
      // deleted when data is removed
      } else {
        Object.defineProperty( owner, this.expando, {
          value: value,
          configurable: true
        } );
      }
    }
  }
  return value;
},

set: function( owner, data, value ) {
  var prop,
    cache = this.cache( owner );
  // Handle: [ owner, key, value ] args
  // Always use camelCase key (gh-2257)
  if ( typeof data === "string" ) {
    cache[ jQuery.camelCase( data ) ] = value;
  // Handle: [ owner, { properties } ] args
  } else {
    // Copy the properties one-by-one to the cache object
    for ( prop in data ) {
      cache[ jQuery.camelCase( prop ) ] = data[ prop ];
    }
  }
  return cache;
},

get: function( owner, key ) {
  return key === undefined ?
    this.cache( owner ) :
    // Always use camelCase key (gh-2257)
    owner[ this.expando ] && owner[ this.expando ][ jQuery.camelCase( key ) ];
},

access: function( owner, key, value ) {
  // In cases where either:
  //
  //  1. No key was specified
  //  2. A string key was specified, but no value provided
  //
  // Take the "read" path and allow the get method to determine
  // which value to return, respectively either:
  //
  //  1. The entire cache object
  //  2. The data stored at the key
  //
  if ( key === undefined ||
      ( ( key && typeof key === "string" ) && value === undefined ) ) {
    return this.get( owner, key );
  }
  // When the key is not a string, or both a key and value
  // are specified, set or extend (existing objects) with either:
  //
  //  1. An object of properties
  //  2. A key and value
  //
  this.set( owner, key, value );
  // Since the "set" path can have two possible entry points
  // return the expected data based on which path was taken[*]
  return value !== undefined ? value : key;
},

remove: function( owner, key ) {
  var i,
    cache = owner[ this.expando ];
  if ( cache === undefined ) {
    return;
  }
  if ( key !== undefined ) {
    // Support array or space separated string of keys
    if ( jQuery.isArray( key ) ) {
      // If key is an array of keys...
      // We always set camelCase keys, so remove that.
      key = key.map( jQuery.camelCase );
    } else {
      key = jQuery.camelCase( key );
      // If a key with the spaces exists, use it.
      // Otherwise, create an array by matching non-whitespace
      key = key in cache ?
        [ key ] :
        ( key.match( rnotwhite ) || [] );
    }
    i = key.length;
    while ( i-- ) {
      delete cache[ key[ i ] ];
    }
  }
  // Remove the expando if there's no more data
  if ( key === undefined || jQuery.isEmptyObject( cache ) ) {
    // Support: Chrome <=35 - 45
    // Webkit & Blink performance suffers when deleting properties
    // from DOM nodes, so set to undefined instead
    // https://bugs.chromium.org/p/chromium/issues/detail?id=378607 (bug restricted)
    if ( owner.nodeType ) {
      owner[ this.expando ] = undefined;
    } else {
      delete owner[ this.expando ];
    }
  }
},　

hasData: function( owner ) {
  var cache = owner[ this.expando ];
  return cache !== undefined && !jQuery.isEmptyObject( cache );
}

dataPriv
  公共
    $.hasData
    $.cleanData
    cloneCopyEvent
  队列
    $().queue
    $()._queueHooks
    $().promise
  动画
    $().animate
    $().stop
    $().finish
    showHide
  事件
    $.event.add
    $.event.remove
    $.event.dispatch
    $.event.trigger
  其它
    setGlobalEval
    domManip
    defaultPrefilter
    $().toggleClass
dataUser
  公共
    $.hasData
    $.cleanData
    cloneCopyEvent
  数据缓存
    $.data
    $.removeData
    $().data
    $().removeData
  其它
    dataAttr

hasData: function( elem ) {
return dataUser.hasData( elem ) || dataPriv.hasData( elem );
},

var cloneNode = $.clone(elem);