node.js cannot parse json - reason: Unexpected token in JSON at position 0

Question

I've been trying for several days but I can't do the diel json parser at this url http://sdmx.istat.it/SDMXWS/rest/dataflow/IT1//?detail=full&references=none&format=jsonstructure

I can write it to a file and if I try to upload the file to one of the many online tools it tells me that it is valid.

Also the url test in the same online tools gives me valid json. this is my code what am I wrong?

    var express = require('express');
var router = express.Router();
const fetch = require('node-fetch');


const JSONstat = require("jsonstat-toolkit");
const JSONstatUtils = require("jsonstat-suite");
const fs = require('fs');

router.get('/', async(req, res) => {
    
    var ws_entry_point ='http://sdmx.istat.it/SDMXWS/rest';
    var resource = 'dataflow';
    var agencyID ='IT1';
    var detail = 'full';
    var references = 'none';
    var format = 'jsonstructure';

    var queryUrl = ws_entry_point + '/' + resource + '/' + agencyID + '//?detail=' + detail + '&references=' + references + '&format=' + format;
    //http://sdmx.istat.it/SDMXWS/rest/dataflow/IT1//?detail=full&references=none&format=jsonstructure
    
    console.log( queryUrl );
    fetch(queryUrl, {
      method: 'GET',
      headers: {
        'Content-Type': 'application/json, charset=UTF-8'
      }}).then(checkResponseStatus)
      .then(async response => {
      try {
       const data = await response.json()
       console.log('response data?', data)
     } catch(error) {
       console.log('Error happened here!')
       console.error(error)
     }
    }).catch(err => console.log(err));

//    fs.writeFile('dataflow.json', res.data, function (err) {
//      if (err) return console.log(err);
//      
//      console.log('write response.text > dataflow.json');
//      fs.readFile('dataflow.json', 'utf8', function (err, dataF) {
//        if (err) throw err; // we'll not consider error handling for now
//        console.log('read  < dataflow.json');
//        //var obj = JSON.parse(dataF);
//        console.log(dataF);
//      });
//    });

  });
  function checkResponseStatus(res) {
    if(res.ok){
        return res
    } else {
        throw new Error(`The HTTP status of the reponse: ${res.status} (${res.statusText})`);
    }
  }

any help is appreciated, regards, Maurizio

eol · Accepted Answer · 2021-03-13 09:48:31Z

2

The server does not respond with the requested application/json content-type, instead it sends a response with content-type application/vnd.sdmx.structure+json and a response content that contains a json-like string but with some incorrect whitespaces.

You can fix this by using .text() on the response and manually parsing the content after trimming it:

const rawData = await response.text();
const data = JSON.parse(rawData.trim());
console.log('response data?', data)

edited Mar 13, 2021 at 9:48

answered Mar 13, 2021 at 9:38

eol

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5 Comments

incal Over a year ago

.trim () was what I was missing! I feel like an idiot I had already tried the response.text () paser many times but without the trim I always had the same error "SyntaxError: Unexpected token in JSON at position" thank you very much

eol Over a year ago

Happy to help, please accept my answer by clicking the checkmark on the left if this solved your issue, thanks!

incal Over a year ago

yes it is the solution for me, I should have accepted your solution

incal Over a year ago

I did it "You last voted on this answer yesterday. Your vote is now locked in unless this answer is edited."

eol Over a year ago

Yes, thanks for the upvote, but there also checkmark symbol you can click to accept the answer - un segno di spunta in italiano.. You may want to read meta.stackexchange.com/questions/5234/…

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