类型错误：res.json 不是函数

Question

I'm trying to send two json but It doesn't work. It prints TypeError: res.json is not a function but I don't get why It happens. Is there any ideas? Thank you !!

app.post('/danger', function response(req, res) {
    let placeId = req.body.data;
    let option = {
      uri: 'https://maps.googleapis.com/maps/api/directions/json?',
      qs: {
        origin:`place_id:${placeId[0]}`, destination: `place_id:${placeId[1]}`,
        language: 'en', mode: 'walking', alternatives: true, key: APIKey
      }
    };
    rp(option)
      .then(function(res) {
        let dangerRate = dangerTest(JSON.parse(res), riskGrid);
        res.json({ data: [res, dangerRate]});
      })
      .catch(function(err) {
        console.error("Failed to get JSON from Google API", err);
      })
});

Answer 1

Because you're overwriting your res variable in the .then of your rp function:

app.post('/danger', function response(req, res) { //see, "res" here was being overwritten
   ..
   ..
   rp(option).then(function(response) { //change the variable name of "res" to "response" (or "turtles", who cares, just dont overwrite your up most "res")

Answer 2

I got this error message because I had the arguments in the wrong order in the handler method. (amateur's fault)

Wrong order: (res, req)

app.get('/json', (res, req) => {
  res.json({
    "message": "Hello json"
  });
});

Right order: (req, res)

app.get('/json', (req, res) => {
  res.json({
    "message": "Hello json"
  });
});

Answer 3

.json isn't a function. Unless you are using a library that makes it one, JavaScript uses JSON (with two methods .parse() and .stringify() one of which you use in the line above).

If you are trying to set an object property by the name of .json then it would be:

res.json = {data: [res, dangerRate]};

Answer 4

使用新的 httpClient 库，您不需要调用 .json() 方法，只需使用这个简单的映射而不是 json 方法。

.map(res => res );

Answer 5

In your case, you write res in nested but if you write a response(res,req) then also get the same error.

So make sure check the sequence

Answer 6

check the sequence=>

If you have write nested res and you write (res,req) you get error.