Debugging JSON Serialization Issues in a Legacy Node.js Application
Could someone explain I'm stuck trying to Working on a legacy Node.js application, I've stumbled across an inconsistency in how JSON is being serialized for a specific object type. The application uses Express and I noticed that when serializing user data, some fields aren't getting included in the output JSON. In particular, the `createdAt` and `updatedAt` timestamps are sometimes omitted, but not consistently. After digging into the code, I found the following serialization logic: ```javascript app.get('/api/users/:id', async (req, res) => { const user = await User.findById(req.params.id); const serializedUser = JSON.stringify(user); res.json(serializedUser); }); ``` This approach works for most users, but I've discovered that the `user` object sometimes has these timestamp fields set as `null`, which leads to them being excluded from the serialized output. To address this, I tried explicitly defining a custom toJSON method in the User schema: ```javascript const userSchema = new mongoose.Schema({ name: String, email: String, createdAt: { type: Date, default: Date.now }, updatedAt: { type: Date, default: Date.now }, }); userSchema.set('toJSON', { transform: (doc, ret) => { ret.createdAt = ret.createdAt || new Date(); ret.updatedAt = ret.updatedAt || new Date(); return ret; } }); ``` This works well for ensuring that the timestamps are always present. However, during testing, I'm still encountering instances where the `updatedAt` field shows up as `undefined`. I placed console logs throughout the code but couldn't capture the root cause. I also checked if the issue could be related to how Mongoose handles updates. I implemented a middleware to update the `updatedAt` field on every save, but the problem persists. The middleware looks like this: ```javascript userSchema.pre('save', function(next) { this.updatedAt = Date.now(); next(); }); ``` Am I missing something in my approach, or is there a deeper issue at play with the way Mongoose interacts with the JSON serialization process? Any insights or debugging tips would be greatly appreciated. I'm open to any suggestions. For context: I'm using Javascript on Linux.