访问 JSON Covid 数据时出现问题

Question

Background on my application

I am using react and node js. I connected node.js to react.js using axios.

Issue

I'm trying to access the cases (5226) in Afganistan, but I can't seem to get the right variable for it.

const cases = covidData[0].cases

Whenever, i try to run the app using nodemon (to run my server) and npm start (to run my react app) I get the following error on my terminal

Error from node terminal

[nodemon] starting `node ./server.js`
listening at port 5000
200
undefined:1
[{"updated":1589436777722,"country":"Afghanistan","countryInfo":{"_id":4,"iso2":"AF","iso3":"AFG","lat":33,"long":65,"flag":"https://disease.sh/assets/img/flags/af.png"},"cases":5226,"todayCases":0,"deaths":132,"todayDeaths":0,"recovered":648,"active":4446,"critical":7,"casesPerOneMillion":134,"deathsPerOneMillion":3,"tests":18724,"testsPerOneMillion":481,"continent":"Asia"},{"updated":1589436777821,"country":"Albania","countryInfo":{"_id":8,"iso2":"AL","iso3":"ALB","lat":41,"long":20,"flag":"https://disease.sh/assets/img/flags/al.png"},"cases":880,"todayCases":0,"deaths":31,"todayDeaths":0,"recovered"


SyntaxError: Unexpected end of JSON input
    at JSON.parse (<anonymous>)
    at IncomingMessage.<anonymous> (/Users/alfietorres/github/covid19/server.js:13:30)
    at IncomingMessage.emit (events.js:198:13)
    at IncomingMessage.Readable.read (_stream_readable.js:504:10)
    at flow (_stream_readable.js:973:34)
    at resume_ (_stream_readable.js:954:3)
    at process._tickCallback (internal/process/next_tick.js:63:19)
[nodemon] app crashed - waiting for file changes before starting...

JSON from website

[
 {
 "updated": 1589433177684,
 "country": "Afghanistan",
 "countryInfo": {
  "_id": 4,
  "iso2": "AF",
  "iso3": "AFG",
  "lat": 33,
  "long": 65,
  "flag": "https://disease.sh/assets/img/flags/af.png"
 },
 "cases": 5226,
 "todayCases": 0,
 "deaths": 132,
 "todayDeaths": 0,
 "recovered": 648,
 "active": 4446,
 "critical": 7,
 "casesPerOneMillion": 134,
 "deathsPerOneMillion": 3,
 "tests": 18724,
 "testsPerOneMillion": 481,
 "continent": "Asia"
 },
 {
.
.
.
etc

Node.js code

const express = require("express");
const app = express();
const https = require("https");

const url = "https://disease.sh/v2/countries/";


app.get("/getData",function(req,res){
  https.get(url, function(response){
      console.log(response.statusCode)

      response.on("data",function(data){
        const covidData=JSON.parse(data)
        // const cases = covidData.cases
        res.send({covidData});
      })

    }, function(err){ console.log(err)})
  }
)


app.listen(5000,function(){
  console.log("listening at port 5000")
})

Answer 1

When you get an issue like this, the first thing to do is to check for the error, in other words add a handler for the error to see what's going wrong

  https.get('https://disease.sh/v2/countries', function(response){
    console.log(response.statusCode)

  }, function(err){ console.log(err)})

The error is connection refused, means it cannot connect to remote server, as you can see you are missing a slash in your url, to fix it:

  https.get('https://disease.sh/v2/countries/', function(response){
    console.log(response.statusCode)

  }, function(err){ console.log(err)})

Or better just use the more clear version of request

const request = require('request');

request('https://disease.sh/v2/countries', function (error, response, body) {
  console.error('error:', error); // Print the error if one occurred
  console.log('statusCode:', response && response.statusCode); // Print the response status code if a response was received
  console.log('body:', JSON.parse(body)[0].cases); // get cases from the country you specified Afghanistan
});

This is from their official docs, I just changed the url to yours.

You can test this request separately by bringing up node in your terminal, just type node and then try the request without the express server.