javascript - Chrome Extension Storing Custom Object Type Strips Prototype Methods -

i have created custom object using in extension. when save objects of type group (my object type) , later pull objects out of storage, appears prototype methods no longer present. read in documentation objects serialize down object literals {} , can't seem figure out how keep methods objects. have provided code of group class below. when try , use 1 of methods file below on object retrieved storage, error function not exist. used in loop loop through of properties , object has name , urls property. appreciated!

group.js:

// create group class var group = function (name, urls) {   this.name = name;   this.urls = urls; };  // clears urls group group.prototype.clearurls = function () {   this.urls = []; };  // adds specified url group group.prototype.addurl = function (url) {   this.urls.append(url); };  // removes specified url group group.prototype.removeurl = function (url) {   this.urls = this.urls.filter(function(_url){     return url !== _url;   }); };  // renames group group.prototype.rename = function (name) {   this.name = name; };  // checks whether or not group contains specified url // returns either true or false group.prototype.containsurl = function (url) {   var contains = false;   (var = 0; < this.urls.length; i++) {     if (this.urls[i] === url) {       contains = true;       break;     }   }   return contains; }; 

edit:

here background.js script, shows how object retrieved , how called later in script. fails when receives addurl message , attempts call containsurl() on currentgroup.

// global variables var currentgroup; var groups = []; var options = [];  // short hand function save current data storage var savedata = function () {   // save default options, currrentgroup, , groups   chrome.storage.sync.set({'options': options, 'currentgroup': currentgroup, 'groups': groups}, function() {     if (chrome.runtime.lasterror) {       console.error("could not save because: " + chrome.runtime.lasterror);     }   }); }  // on start query saved data make sure data current chrome.storage.sync.get(function(items) {   // check if there groups   if (items['groups']) { // set groups     groups = items['groups'];   } else { // create default group , add list of groups     currentgroup = new group('default', []);     groups = [currentgroup];   }    // check current group, if none set first available group   if (items['currentgroup']) {     currentgroup = items['currentgroup'];     console.log(object.getownpropertynames(currentgroup));   } else {     currentgroup = groups[0];   }    // check options   if (items['options']) {     options = items['options'];   } else {     // no options, set default options , save them     options['overridehomepages'] = true;   }    savedata();    // after data has been fetched bring tabs   chrome.tabs.query({'currentwindow': true}, function(tabs) {     (var = 0; < currentgroup.urls.length; i++) {       if (options['overridehomepages']) {         if (tabs[i].url.length > 0) {           chrome.tabs.update(tabs[0].id, {'url': currentgroup.urls[i]});         } else {           chrome.tabs.create({'url': currentgroup.urls[i]});         }       } else { // don't override homepages or open tabs         chrome.tabs.create({'url': currentgroup.urls[i]});       }       currentgroup.urls[i]     }   }); // end tabs.query  }); // end storage.sync.get  // add message listener chrome.runtime.onmessage.addlistener(function(request, sender, sendresponse) {    // if add url sent   if (request.message === 'addurl') {     console.log('recieved message: ' + request.message);     // check if group contains url     if (currentgroup.containsurl(sender.url) === false) {       currentgroup.addurl(sender.url);       savedata();       sendresponse({'message': 'saved ' + sender.url});     }   }    // if remove url sent   if (request.message === 'removeurl') {     // check if group contains url     if (currentgroup.containsurl(sender.url)) {       currentgroup.removeurl(sender.url);       savedata();       sendresponse({'message': 'removed ' + sender.url})     }   } }); 

i believe chrome.storage used save key-value items, not including prototype/functions. however, didn't find official docs this.

one workaround using group.prototype.containsurl.call(currentgroup, sender.url), allows invoke containsurl specifying context "this".