使用$set结合stringify失效，Express接口报语法错误求助

Hey there! Let's work through your issues one by one—first that annoying syntax error stopping your PUT interface, then figuring out why your $set + stringify approach isn't updating your MongoDB data.

1. Fix the "missing ) after argument list" Syntax Error #

Looking at your code, two immediate syntax issues are causing that error:

• You left off the closing parentheses for the FacturaModel constructor and the route callback function.
• The ... after factura.nombre is invalid syntax here (unless you meant to spread an array/object, but that's not what your code is doing right now).

Here's the corrected code snippet for the route structure:

app.put('/factura/:id', (req, res) => {
  res.header({'Content-Type': 'application/json'});
  var factura = req.body;
  // Fixed: Closed all parentheses and removed invalid ...
  var facturaModel = new FacturaModel({ 
    nro: factura.nro, 
    nit: factura.nit, 
    cliente: factura.cliente, 
    tarjeta: factura.tarjeta, 
    detalles: [{producto: factura.nombre}] 
  });
  // We'll add proper update logic below
});

2. Correct Way to Update MongoDB Data with $set #

The bigger issue is that your current code creates a new FacturaModel instance (which would insert a new document), not update the existing one with the :id from the URL. That's why your $set attempts weren't working—you weren't targeting the right document.

Here's how to fix this properly:

Step 1: Ensure Request Body Parsing #

First, make sure you've enabled JSON body parsing in Express (required to access req.body correctly):

// Add this at the top of your file, before defining routes
app.use(express.json());

You won't need JSON.stringify here—Express handles parsing the incoming JSON request body into a JavaScript object automatically.

Step 2: Use findByIdAndUpdate with $set #

Replace your route code with this, which targets the specific document by ID and uses $set to update only the fields you want:

app.put('/factura/:id', async (req, res) => {
  try {
    const facturaId = req.params.id;
    // Define the fields you want to update
    const updateFields = {
      nro: req.body.nro,
      nit: req.body.nit,
      cliente: req.body.cliente,
      tarjeta: req.body.tarjeta,
      detalles: [{producto: req.body.nombre}]
    };

    // Update the document: $set ensures only specified fields are changed
    const updatedFactura = await FacturaModel.findByIdAndUpdate(
      facturaId,
      { $set: updateFields },
      { 
        new: true, // Return the updated document instead of the original
        runValidators: true // Ensure your schema validation rules are applied
      }
    );

    // Handle case where no document matches the ID
    if (!updatedFactura) {
      return res.status(404).json({ message: "Factura not found" });
    }

    res.json(updatedFactura);
  } catch (error) {
    res.status(500).json({ message: error.message });
  }
});

3. Why Your Original Approach Failed #

• Creating new FacturaModel() is for inserting new documents, not updating existing ones. It has no connection to the :id in your URL.
• Using JSON.stringify was unnecessary because Express already parses the request body into a usable object. If you tried to stringify and then pass it to MongoDB, it would store a string instead of structured data, which isn't what you want.
• $set only works in MongoDB update operations (like findByIdAndUpdate or updateOne), not when creating new model instances.

内容的提问来源于stack exchange，提问作者Feber Castellon