How to parse JSON object to CSV file using json2csv nodejs module

Question

I'm currently learning how to parse a JSON object to a CSV file using the json2csv node module. Have never worked with JSON before, so this is all new to me.

My JSON object is formatted like this:

{
 "car":
      {
          "name":["Audi"],
          "price":["40000"],
          "color":["blue"]
      }
}

And the output CSV file is formatted like this:

"car","name","price","color"
{"name":["Audi"],"price":["40000"],"color":["blue"]},,,

How would I be able to get the CSV output to look like this instead?

name, price, color
"Audi",40000,"blue"

I understand I can call fields directly for just regular JSON data, but I don't understand how it would work under a JSON object.

Answer 1

json2csv only support a flat structure where fields are direct children of the json root.

if you wish to change it, consider cloning the code and do something like the following:

// createColumnContent function changed from original code
var createColumnContent = function(params, str, callback) {
  params.data.forEach(function(data_element) {
    //if null or empty object do nothing
    if (data_element && Object.getOwnPropertyNames(data_element).length > 0) {
      var line = '';
      var eol = os.EOL || '\n';
      params.fields.forEach(function(field_element) {
        // here, instead of direct child, getByPath support multiple subnodes levels
        line += getByPath(data_element, field_element.split('.'), 0) + params.del;
      });
      //remove last delimeter
      line = line.substring(0, line.length - 1);
      line = line.replace(/\\"/g, '""');
      str += eol + line;
    }
  });
  callback(str);
};

var getByPath = function(data_element, path, position) {
  if (data_element.hasOwnProperty(path[position])) {
    if (position === path.length - 1) {
      return JSON.stringify(data_element[path[position]]);
    }
    else {
      return getByPath(data_element[path[position]], path, position + 1)
    }
  }
  else {
    return '';
  }
}

usage:

json2csv({data: json, fields: ['car.name.0', 'car.price.0', 'car.color.0']}, function(err, csv) {
  if (err) console.log(err);
  fs.writeFile('file.csv', csv, function(err) {
    if (err) throw err;
    console.log('file saved');
  });
});

output file content:

"car.name.0","car.price.0","car.color.0"
"Audi","40000","blue"

as a side note, to clone and work with your own version:

git clone https://github.com/zeMirco/json2csv.git

add changes...

to use changed version:

npm install /local/path/to/repo

Answer 2

You can also direct json2csv to use a sub array within your JSON object by addressing it with .<name> after your JSON object in the data section of json2csv.

In your case, this might look something like:

const json2csv = require('json2csv');
const fs = require('fs');

var json = {
 "car":[
  {
   "name":"Audi",
   "price":"40000",
   "color":"blue"
  }
 ]
};

json2csv({data: json.car, fields: ['name', 'price', 'color']}, function(err, csv) {
  if (err) console.log(err);
  fs.writeFile('cars.csv', csv, function(err) {
    if (err) throw err;
    console.log('cars file saved');
  });
});

Answer 3

const { Parser } = require('json2csv');

let myCars = {
    "car":
    {
        "name": ["Audi"],
        "price": ["40000"],
        "color": ["blue"]
    }
};

let fields = ["car.name", "car.price", "car.color"];

const parser = new Parser({
    fields,
    unwind: ["car.name", "car.price", "car.color"]
});

const csv = parser.parse(myCars);

console.log('output',csv);

will output to console

Answer 4

The input is bad format, it should like json2csv document:

var json2csv = require('json2csv');

var json = [
  {
    "car": "Audi",
    "price": 40000,
    "color": "blue"
  }, {
    "car": "BMW",
    "price": 35000,
    "color": "black"
  }, {
    "car": "Porsche",
    "price": 60000,
    "color": "green"
  }
];

json2csv({data: json, fields: ['car', 'price', 'color']}, function(err, csv) {
  if (err) console.log(err);
  fs.writeFile('file.csv', csv, function(err) {
    if (err) throw err;
    console.log('file saved');
  });
});

The content of the "file.csv" should be

car,       price, color
"Audi",    40000, "blue"
"BMW",     35000, "black"
"Porsche", 60000, "green"

Answer 5

I was able to solve this using the parse method and formatting my json data as an array of objects.

const { parse, Parser } = require('json2csv');
const data = [
     {key: value, key2: value2 },
     {key: value3, key2: value4 }
     ];
const fields = ['key', 'key2'];
const csv = parse(data, { fields });

Then do what you need with the csv variable.

Answer 6

I don't know about you guys, but i like small packages that just work as expected without a lot of extra configuration, try using jsonexport, works really well with objects, arrays, .. and its fast!

Install

npm i --save jsonexport

Usage

const jsonexport = require('jsonexport');
const fs = require('fs');

jsonexport({
 "car":[
  {
   "name":"Audi",
   "price":"40000",
   "color":"blue"
  }
 ]
}, function(err, csv) {
  if (err) return console.error(err);
  fs.writeFile('cars.csv', csv, function(err) {
    if (err) return console.error(err);
    console.log('cars.csv saved');
  });
});

https://github.com/kauegimenes/jsonexport

Answer 7

Check out Underscore.js pluck method - if you pass _.pluck(json, 'car') to json2csv's data instead of the original json, you should get what you're looking for.