code: function db(op, fn){
    if(!indexedDB){
      return fn(new Error('store `indexeddb` not supported by this browser'));
    }
    if(typeof op === 'function'){
      fn = op;
      op = 'readwrite';
    }
  
    if(source !== null){
      return fn(null, source.transaction(module.exports.prefix, op).objectStore(module.exports.prefix));
    }
    var req = indexedDB.open(module.exports.prefix, 1);
    req.onerror = function(e){
      fn(e);
    };
    req.onupgradeneeded = function(){
      // First time setup: create an empty object store
      req.result.createObjectStore(module.exports.prefix);
    };
    req.onsuccess = function() {
      source = req.result;
      db(op, fn);
    };
  }
docs: Wrapper function that handles creating or acquiring the object store if it hasn't been already.