google chrome - passing data from contentscripts.js to popup.js via storage local -

i'm still busy first extension. want pass on data (an array) contentscripts.js popup.js. read in several sources easiest way using local storage.

this tried:

contentscripts.js (i don't know if 1 works)

... alert(isotopeindices[0]);  // array isotopeindices has lots entries chrome.storage.local.set(isotopeindices[0]);  //goal save whole array: chrome.storage.local.set(isotopeindices); 

popup.js

chrome.storage.local.get(     function(isotopeindices) {         document.getelementbyid('selectisotopes').innerhtml = isotopeindices[0];     } ); 

my popup shows in <div id="selectisotopes">...</div>-element undefined. why think chrome.storage.local.set doesn't work @ all. concerning google-howto (http://developer.chrome.com/extensions/storage.html) should correct.

even though question is, local storage simplest way pass data...?

thanks time , help!!!