=> { const afterData = new firestoreModels.MapComment(change.after.data()); const afterLike = afterData.likeMembers.length; const beforeData = new firestoreModels.MapComment(change.before.data()); const beforeLike = beforeData.likeMembers.length; const toUserId = afterData.user; if (!toUserId) return null; if (beforeLike < afterLike) { return pushMessageByUserId(toUserId, '͍͍Ͷ͕ԡ͞Ε·ͨ͠ʂ'); } return null; });