react-native fetch return status code + json

问题:

I use fetch in react-native to make API calls.

I need to get status code (200 , 401, 404 ) and the response data.

This work to get the response data :

return fetch(url)
.then(response => {
  return response.json();
})
.then(res => {
  console.log("reponse :", res); // <-------- res is ok with data
 })    .catch(error => {
  console.error(error);
  return { name: "network error", description: "" };
});

Now i tweak the first then to get the status code but data is not what i except

return fetch(url)
.then(response => {
  const statusCode = response.status;
  const data = response.json();
  return { statusCode, data };
})
.then(res => {
  console.log("reponse :", res); // <-------- i get a "promise"
 }).catch(error => {
  console.error(error);
  return { name: "network error", description: "" };
});

the console log :

  {statusCode: 200, data: Promise}

回答1:

response.json() returns a promise, you should wait until it will be fulfilled. To do that you can use Promise.all with array of two elements: statusCode and response.json() call:

return fetch(url)
  .then(response => {
    const statusCode = response.status;
    const data = response.json();
    return Promise.all([statusCode, data]);
  })
  .then([res, data] => {
    console.log(res, data);
  })
  .catch(error => {
    console.error(error);
    return { name: "network error", description: "" };
  });

//EDIT you can create a function who process the response

function processResponse(response) {
  const statusCode = response.status;
  const data = response.json();
  return Promise.all([statusCode, data]).then(res => ({
    statusCode: res[0],
    data: res[1]
  }));
}

and use it the then()

 return fetch(url)
    .then(processResponse)
    .then(res => {
        const { statusCode, data } = res;
        console.log("statusCode",statusCode);
        console.log("data",data);
    }) .catch(error => {
    console.error(error);
    return { name: "network error", description: "" };
  });

回答2:

Because the response of the API in the first then is a string not an object, you can't use the response like response.status. You should first convert the response to a JSON object and then use the status as response.status like the first example. The code should work properly:

return fetch(url)
.then(response => {
  const statusCode = response.status;
  let data;
  response.json().then(obj=>{
    data= obj;
    return { statusCode, data };
  });

})
.then(res => {
  console.log("reponse :", res); // <-------- i get a "promise"
 }).catch(error => {
  console.error(error);
  return { name: "network error", description: "" };
});