'ERR_HTTP_HEADERS_SENT' 在 Node.js/Express 应用中的 POST 请求之后，请求 http 客户端

Question

The line res.send("Successfully saved the new address."); throws the 'ERR_HTTP_HEADERS_SENT' error.

I read through other posts concerning the same error and tried return res.send("Successfully saved the new address.") , but that doesn't fix it. Any insights?

Note: I am new to this.

Please be kind.

Thanks.

My Code

app.post("/", function(req, res) {
  const url = "http://geocode.arcgis.com/arcgis/rest/services/World/GeocodeServer/findAddressCandidates?";
  const street = req.body.street;
  const city = req.body.city;
  const state = req.body.state;
  const zip = req.body.zip;

  const yourAddress = "Address=" + street.replace(" ", "+") + "&City=" + city.replace(" ", "+") + "&Zip=" + zip;
  const parameters = "&category=&outFields=*&forStorage=false&f=json";

  request(url + yourAddress + parameters, function(error, response, body) {
    const data = JSON.parse(body);

    const newAddress = data.candidates[0].address;
    const longitude = data.candidates[0].location.x;
    const latitude = data.candidates[0].location.y;

    const address = new Address({
      address: newAddress,
      latitude: latitude,
      longitude: longitude
    });

    address.save(function(err) {
      if (!err) {
        res.send("Successfully saved the new address.");
      } else {
        res.send(err);
      }
    });
  });
  res.redirect("/");
});

Answer 1

You are doing both res.send() and res.redirect() in the same request handler. You can't send two responses to the same request. That's what generates the warning message you see.

Pick one of the other. You either want to send an appropriate status about the .save() or you want to redirect. One or the other, not both.

In this particular code, the res.redirect() happens first so it's what the client sees. Then, after that and when the request() and the address.save() have both completed, then you try to res.send() , but that is blocked because a response has already been sent and the http connection is already done.

If you just want to redirect upon successful save, you can remove the existing res.redirect() and change to this:

address.save(function(err) {
  if (!err) {
    res.redirect("/");
  } else {
    console.log(err);
    res.sendStatus(500);
  }

Answer 2

I would Agree With @jfriend00 answer , since there can be only one response for the request . Here's what you can do:

address.save(function(err) {
  if (!err) {
    res.redirect('/success')
  } else {
    res.send(err);
  }
});
//add a new route
     app.get('/success',(req,res)=>{res.send('Successfully saved the new address.')})

And then you can redirect to the home page.

This is just a workaround in this case and can differ logically in each case depending on the requirement

The Other Way is to redirect on the client side itself eg:If you're on jquery

 $.ajax({
      statusCode: {
        200: function() {
         $(location).attr('href', 'to the homepage')
        }
      }
    });