jQuery data() returns undefined -

i use jquery data() store meta data, seems jquery 1.4.4 , 1.4.3 both have problems. parts work , other parts not work.

for instance, have

const uimconst = {     node_object: "nodeobject",     children: "children",     parent: "parent",     sid: "sid",     count: "count",     exclude: "exclude",     parent_count: "pcount",     height: "uimheight" };  workspace.prototype.findancestor = function(element){     if(this.ancestor == null){         this.ancestor = $(element);         this.ancestor.data(uimconst.height, 0);     } else { ...  } 

where element dom element. then, value stored follows,

var height = this.ancestor.data(uimconst.height); logger.debug("current ui module height " + height); 

unfortunately, return value undefined.

to further trace problem, changed code be

if(this.ancestor == null){     this.ancestor = $(element);     this.ancestor.data(uimconst.height, 0);     logger.debug("after set ancestor height, value " +   this.ancestor.data(uimconst.height)); } else { 

the return value in log "undefined" well. frustrated.

i used data() in other places , worked fine. not sure happened. hints?

the project here if wants take look:

http://aost.googlecode.com/svn/trunk/tools/tellurium-ide.

just subversion check out , run following command:

mvn install 

and install generated .xpi file firefox.

after that, can open tellurium ide firefox plugin , javascript debugger firefox plugin track execution.

for problem, go workspace.js , set breakpointer @ beginning of findancestor() method.

more details tellurium ide here:

http://code.google.com/p/aost/wiki/telluriumide080rc1

thanks in advance,

john

this happen if element null, or string did not match elements in document.

$(element).data(key, value) nothing if $(element).length == 0.

jquery silently refuses store data on elements (embed, applet, , object except flash), doesn't seem problem.

update: if firefox add-on code trying operate on elements in web page, it's no big surprise me doesn't work. elements behave bit differently when used add-on, libraries (like jquery) work great in normal web pages can fail work in add-ons.

update 2: new advice use development version of jquery, such http://code.jquery.com/jquery-latest.js , , step through data method in debugger. interesting parts happen in jquery.data, on 40 lines long:

data: function( elem, name, data ) {     [...]      var isnode = elem.nodetype,         id = isnode ? elem[ jquery.expando ] : null,         cache = jquery.cache, thiscache;      if ( isnode && !id && typeof name === "string" && data === undefined ) {         return;     }      // data object directly     if ( !isnode ) {         cache = elem;      // compute unique id element     } else if ( !id ) {         elem[ jquery.expando ] = id = ++jquery.uuid;     }      // avoid generating new cache unless none exists ,     // want manipulate it.     if ( typeof name === "object" ) {         if ( isnode ) {             cache[ id ] = jquery.extend(cache[ id ], name);          } else {             jquery.extend( cache, name );         }      } else if ( isnode && !cache[ id ] ) {         cache[ id ] = {};     }      thiscache = isnode ? cache[ id ] : cache;      // prevent overriding named cache undefined values     if ( data !== undefined ) {         thiscache[ name ] = data;     }      return typeof name === "string" ? thiscache[ name ] : thiscache; },