Function key

src/js/libraries/localbase.js:2155–2214

(n, callback)

}

function key(n, callback) {
    var self = this;

    var promise = new Promise$1(function (resolve, reject) {
        if (n < 0) {
            resolve(null);

            return;
        }

        self.ready().then(function () {
            createTransaction(self._dbInfo, READ_ONLY, function (err, transaction) {
                if (err) {
                    return reject(err);
                }

                try {
                    var store = transaction.objectStore(self._dbInfo.storeName);
                    var advanced = false;
                    var req = store.openKeyCursor();

                    req.onsuccess = function () {
                        var cursor = req.result;
                        if (!cursor) {
                            // this means there weren't enough keys
                            resolve(null);

                            return;
                        }

                        if (n === 0) {
                            // We have the first key, return it if that's what they
                            // wanted.
                            resolve(cursor.key);
                        } else {
                            if (!advanced) {
                                // Otherwise, ask the cursor to skip ahead n
                                // records.
                                advanced = true;
                                cursor.advance(n);
                            } else {
                                // When we get here, we've got the nth key.
                                resolve(cursor.key);
                            }
                        }
                    };

                    req.onerror = function () {
                        reject(req.error);
                    };
                } catch (e) {
                    reject(e);
                }
            });
        })["catch"](reject);
    });

    executeCallback(promise, callback);