错误 [ERR_HTTP_HEADERS_SENT]：无法在将标头发送到客户端后设置标头，我无法将表单发送到实时数据库

Question

1. this my html code submit

<form action="/user/product/add" method="POST" enctype="multipart/form-data" >
                        <h1 class="h">Add Product</h1>
                        <div>
                            <table class="tableez" cellpadding="4" cellspacing="0" style="width:400px">
                                <tr>
                
                                    <div class="form-group">
                                        <input type="file" name="imageProduct" multiple>
                                    </div>
                                </tr>
                                <tr>
                                    <td class="tdtitle">Tên sản phẩm: </td>
                                    <td><input type="text" value="{{data.nameProduct}}" name="nameProduct"
                                            id="nameProduct">
                                    </td>
                                </tr>
                        <button type="submit" class="btn btn-primary">Thêm</button>
                    </form>

2. this is my api

router.post('/product/add', upload.array('imageProduct', 5), isLoggedIn, function (req, res, next) {
 
    var idd = "5ea4528ccaf1ab0017e0fe22";
    var filesImage = req.files;
    var images = [];
    filesImage.forEach(function (item, index, array) {
      images.unshift(item.filename);
    });
    var winner = [];
    winner.unshift("1");
    winner.unshift("Chưa có");
    //  var messages = [];
    // messages.unshift({
    //     a : "qwe",
    //     b : "asdq"
    // });

    var played = [];
    played.unshift("null");
    var registerDatee = Date.now();
    var time = req.body.time;
    console.log(time);
    const product = {
      imageProduct: images,
      nameProduct: req.body.nameProduct,
      userId: idd,
      nameProductType: req.body.cars,
      startPriceProduct: req.body.currentPrice,
      status: req.body.status,
      description: req.body.description,
      extraTime: req.body.time,
      registerDate: registerDatee,
      winner: winner,
      hide: false,
      currentPrice: req.body.currentPrice,
      played: played
    };

    var db = Firebase.database();
    var rootRef = db.ref('products');
    rootRef.push(product);
    res.redirect('/');

});

After I clicked submit, the following error occurred 3. this is my error

POST /user/product/add 200 151.592 ms - -
_http_outgoing.js:526
    throw new ERR_HTTP_HEADERS_SENT('set');
    ^

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:526:11)
    at ServerResponse.header (C:\Users\HaAnh\Desktop\api\backend-app-daugia\node_modules\express\lib\response.js:767:10)
    at ServerResponse.contentType (C:\Users\HaAnh\Desktop\api\backend-app-daugia\node_modules\express\lib\response.js:595:15)
    at ServerResponse.send (C:\Users\HaAnh\Desktop\api\backend-app-daugia\node_modules\express\lib\response.js:145:14)
    at done (C:\Users\HaAnh\Desktop\api\backend-app-daugia\node_modules\express\lib\response.js:1004:10)
    at Immediate._onImmediate (C:\Users\HaAnh\Desktop\api\backend-app-daugia\node_modules\express-handlebars\lib\utils.js:26:4)
    at processImmediate (internal/timers.js:456:21) {
  code: 'ERR_HTTP_HEADERS_SENT'
}
[nodemon] app crashed - waiting for file changes before starting...

I do not understand why I submitted an error after I submitted it, but it is okay to fix, I have read a lot of the above questions, but there is still no solution for my project. I'm crying because I don't know what to do next. Although an error has occurred, the product has been saved in the database. Please give me a solution so I can continue working on my project!

Answer 1

This looks to be a classic issue with non-blocking I/O in Node. You will need to wrap your work in a Promise.

new Promise(function(resolve, reject) {
  //do the file work
  var idd = "5ea4528ccaf1ab0017e0fe22";
  var filesImage = req.files;
  var images = [];
  filesImage.forEach(function (item, index, array) {
    images.unshift(item.filename);
  });
  // more work here
  return true; //after the work is done
})
.then(() => {
  // do more work here if needed
});
.then(() => {
  // after the I/O work is done
  res.redirect('/');
});

I didn't double check the syntax, but you can get the idea from my snippet.

Answer 2

I suspect that the middleware isLoggedIn returns a response in certain cases (if you have try/catch - what are you doing in the catch?).

These are the cases where the execution path tries to resend the response (both in the middleware as well as here in the code) and hence the error.