json2csv

What is json2csv?

The json2csv npm package is a powerful tool for converting JSON data to CSV format. It is widely used for data transformation and export tasks, making it easier to handle JSON data in a tabular format.

What are json2csv's main functionalities?

Convert JSON to CSV

This feature allows you to convert a JSON array into a CSV string. The code sample demonstrates how to use the `parse` function from the json2csv package to transform a JSON array into CSV format.

const { parse } = require('json2csv');
const json = [{ "name": "John", "age": 30 }, { "name": "Jane", "age": 25 }];
const csv = parse(json);
console.log(csv);

Customizing CSV Fields

This feature allows you to specify which fields to include in the CSV output. The code sample shows how to define a list of fields and pass them as options to the `parse` function.

const { parse } = require('json2csv');
const json = [{ "name": "John", "age": 30 }, { "name": "Jane", "age": 25 }];
const fields = ['name', 'age'];
const opts = { fields };
const csv = parse(json, opts);
console.log(csv);

Handling Nested JSON Objects

This feature allows you to handle nested JSON objects and flatten them into CSV format. The code sample demonstrates how to specify nested fields in the options to correctly map them to CSV columns.

const { parse } = require('json2csv');
const json = [{ "name": "John", "address": { "city": "New York", "state": "NY" } }, { "name": "Jane", "address": { "city": "San Francisco", "state": "CA" } }];
const fields = ['name', 'address.city', 'address.state'];
const opts = { fields };
const csv = parse(json, opts);
console.log(csv);

Other packages similar to json2csv

csv-writer

The csv-writer package provides a simple and flexible way to write CSV files. It supports writing both objects and arrays to CSV, and allows for customization of headers and field delimiters. Compared to json2csv, csv-writer focuses more on writing CSV files rather than converting JSON to CSV strings.

fast-csv

The fast-csv package is a comprehensive library for parsing and formatting CSV files. It offers high performance and a wide range of features, including support for streaming and handling large datasets. While json2csv is primarily focused on converting JSON to CSV, fast-csv provides more extensive functionality for working with CSV data in general.

papaparse

The papaparse package is a powerful CSV parser that can handle large files and supports various configurations for parsing and formatting. It is known for its speed and reliability. Unlike json2csv, which is mainly used for converting JSON to CSV, papaparse excels at parsing CSV files into JSON and other formats.

README

json2csv

Converts json into csv with column titles and proper line endings. Can be used as a module and from the command line.

See the CHANGELOG for details about the latest release.

How to use

Install

$ npm install json2csv --save

Include the module and run or use it from the Command Line. It's also possible to include json2csv as a global using an HTML script tag, though it's normally recommended that modules are used.

var json2csv = require('json2csv');
var fields = ['field1', 'field2', 'field3'];

try {
  var result = json2csv({ data: myData, fields: fields });
  console.log(result);
} catch (err) {
  // Errors are thrown for bad options, or if the data is empty and no fields are provided.
  // Be sure to provide fields if it is possible that your data array will be empty.
  console.error(err);
}

Features

• Uses proper line endings on various operating systems
• Handles double quotes
• Allows custom column selection
• Allows specifying nested properties
• Reads column selection from file
• Pretty writing to stdout
• Supports optional custom delimiters
• Supports optional custom eol value
• Supports optional custom quotation marks
• Not create CSV column title by passing hasCSVColumnTitle: false, into params.
• If field is not exist in object then the field value in CSV will be empty.
• Preserve new lines in values. Should be used with \r\n line endings for full compatibility with Excel.
• Add a BOM character at the beginning of the csv to make Excel displaying special characters correctly.

Use as a module

Available Options

• options - Required; Options hash.
  • data - Required; Array of JSON objects.
  • fields - Array of Objects/Strings. Defaults to toplevel JSON attributes. See example below.
  • fieldNames Array of Strings, names for the fields at the same indexes. Must be the same length as fields array. (Optional. Maintained for backwards compatibility. Use fields config object for more features)
  • del - String, delimiter of columns. Defaults to , if not specified.
  • defaultValue - String, default value to use when missing data. Defaults to <empty> if not specified. (Overridden by fields[].default)
  • quotes - String, quotes around cell values and column names. Defaults to " if not specified.
  • doubleQuotes - String, the value to replace double quotes in strings. Defaults to 2xquotes (for example "") if not specified.
  • hasCSVColumnTitle - Boolean, determines whether or not CSV file will contain a title column. Defaults to true if not specified.
  • eol - String, it gets added to each row of data. Defaults to `` if not specified.
  • newLine - String, overrides the default OS line ending (i.e. \n on Unix and \r\n on Windows).
  • flatten - Boolean, flattens nested JSON using flat. Defaults to false.
  • unwindPath - Array of Strings, creates multiple rows from a single JSON document similar to MongoDB's $unwind
  • excelStrings - Boolean, converts string data into normalized Excel style data.
  • includeEmptyRows - Boolean, includes empty rows. Defaults to false.
  • preserveNewLinesInValues - Boolean, preserve \r and \n in values. Defaults to false.
  • withBOM - Boolean, with BOM character. Defaults to false.
• callback - function (error, csvString) {}. If provided, will callback asynchronously. Only supported for compatibility reasons.

Example fields option

{
  fields: [
    // Supports label -> simple path
    {
      label: 'some label', // (optional, column will be labeled 'path.to.something' if not defined)
      value: 'path.to.something', // data.path.to.something
      default: 'NULL' // default if value is not found (optional, overrides `defaultValue` for column)
    },

    // Supports label -> derived value
    {
      label: 'some label', // Supports duplicate labels (required, else your column will be labeled [function])
      value: function(row, field, data) {
        // field = { label, default }
        // data = full data object
        return row.path1 + row.path2;
      },
      default: 'NULL', // default if value function returns null or undefined
      stringify: true // If value is function use this flag to signal if resulting string will be quoted (stringified) or not (optional, default: true)
    },

    // Support pathname -> pathvalue
    'simplepath', // equivalent to {value:'simplepath'}
    'path.to.value' // also equivalent to {label:'path.to.value', value:'path.to.value'}
  ]
}

Example 1

var json2csv = require('json2csv');
var fs = require('fs');
var fields = ['car', 'price', 'color'];
var myCars = [
  {
    "car": "Audi",
    "price": 40000,
    "color": "blue"
  }, {
    "car": "BMW",
    "price": 35000,
    "color": "black"
  }, {
    "car": "Porsche",
    "price": 60000,
    "color": "green"
  }
];
var csv = json2csv({ data: myCars, fields: fields });

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"

Example 2

Similarly to mongoexport you can choose which fields to export. Note: this example uses the optional callback format.

var json2csv = require('json2csv');
var fields = ['car', 'color'];

json2csv({ data: myCars, fields: fields }, function(err, csv) {
  if (err) console.log(err);
  console.log(csv);
});

Results in

car, color
"Audi", "blue"
"BMW", "black"
"Porsche", "green"

Example 3

Use a custom delimiter to create tsv files. Add it as the value of the del property on the parameters:

var json2csv = require('json2csv');
var fields = ['car', 'price', 'color'];
var tsv = json2csv({ data: myCars, fields: fields, del: '\t' });

console.log(tsv);

Will output:

car price color
"Audi"  10000 "blue"
"BMW" 15000 "red"
"Mercedes"  20000 "yellow"
"Porsche" 30000 "green"

If no delimiter is specified, the default , is used

Example 4

You can choose custom column names for the exported file.

var json2csv = require('json2csv');
var fields = ['car', 'price'];
var fieldNames = ['Car Name', 'Price USD'];
var csv = json2csv({ data: myCars, fields: fields, fieldNames: fieldNames });

console.log(csv);

Example 5

You can choose custom quotation marks.

var json2csv = require('json2csv');
var fields = ['car', 'price'];
var fieldNames = ['Car Name', 'Price USD'];
var opts = {
  data: myCars,
  fields: fields,
  fieldNames: fieldNames,
  quotes: ''
};
var csv = json2csv(opts);

console.log(csv);

Results in

Car Name, Price USD
Audi, 10000
BMW, 15000
Porsche, 30000

Example 6

You can also specify nested properties using dot notation.

var json2csv = require('json2csv');
var fs = require('fs');
var fields = ['car.make', 'car.model', 'price', 'color'];
var myCars = [
  {
    "car": {"make": "Audi", "model": "A3"},
    "price": 40000,
    "color": "blue"
  }, {
    "car": {"make": "BMW", "model": "F20"},
    "price": 35000,
    "color": "black"
  }, {
    "car": {"make": "Porsche", "model": "9PA AF1"},
    "price": 60000,
    "color": "green"
  }
];
var csv = json2csv({ data: myCars, fields: fields });

fs.writeFile('file.csv', csv, function(err) {
  if (err) throw err;
  console.log('file saved');
});

The content of the "file.csv" should be

car.make, car.model, price, color
"Audi", "A3", 40000, "blue"
"BMW", "F20", 35000, "black"
"Porsche", "9PA AF1", 60000, "green"

Example 7

You can unwind arrays similar to MongoDB's $unwind operation using the unwindPath option.

var json2csv = require('json2csv');
var fs = require('fs');
var fields = ['carModel', 'price', 'colors'];
var myCars = [
  {
    "carModel": "Audi",
    "price": 0,
    "colors": ["blue","green","yellow"]
  }, {
    "carModel": "BMW",
    "price": 15000,
    "colors": ["red","blue"]
  }, {
    "carModel": "Mercedes",
    "price": 20000,
    "colors": "yellow"
  }, {
    "carModel": "Porsche",
    "price": 30000,
    "colors": ["green","teal","aqua"]
  }
];
var csv = json2csv({ data: myCars, fields: fields, unwindPath: 'colors' });

fs.writeFile('file.csv', csv, function(err) {
  if (err) throw err;
  console.log('file saved');
});

The content of the "file.csv" should be

"carModel","price","colors"
"Audi",0,"blue"
"Audi",0,"green"
"Audi",0,"yellow"
"BMW",15000,"red"
"BMW",15000,"blue"
"Mercedes",20000,"yellow"
"Porsche",30000,"green"
"Porsche",30000,"teal"
"Porsche",30000,"aqua"

Example 8

You can also unwind arrays multiple times or with nested objects.

var json2csv = require('json2csv');
var fs = require('fs');
var fields = ['carModel', 'price', 'items.name', 'items.color', 'items.items.position', 'items.items.color'];
var myCars = [
  {
    "carModel": "BMW",
    "price": 15000,
    "items": [
      {
        "name": "airbag",
        "color": "white"
      }, {
        "name": "dashboard",
        "color": "black"
      }
    ]
  }, {
    "carModel": "Porsche",
    "price": 30000,
    "items": [
      {
        "name": "airbag",
        "items": [
          {
            "position": "left",
            "color": "white"
          }, {
            "position": "right",
            "color": "gray"
          }
        ]
      }, {
        "name": "dashboard",
        "items": [
          {
            "position": "left",
            "color": "gray"
          }, {
            "position": "right",
            "color": "black"
          }
        ]
      }
    ]
  }
];
var csv = json2csv({ data: myCars, fields: fields, unwindPath: ['items', 'items.items'] });

fs.writeFile('file.csv', csv, function(err) {
  if (err) throw err;
  console.log('file saved');
});

The content of the "file.csv" should be

"carModel","price","items.name","items.color","items.items.position","items.items.color"
"BMW",15000,"airbag","white",,
"BMW",15000,"dashboard","black",,
"Porsche",30000,"airbag",,"left","white"
"Porsche",30000,"airbag",,"right","gray"
"Porsche",30000,"dashboard",,"left","gray"
"Porsche",30000,"dashboard",,"right","black"

Command Line Interface

json2csv can also be called from the command line if installed with -g.

Usage: json2csv [options]

  Options:

    -h, --help                   output usage information
    -V, --version                output the version number
    -i, --input <input>          Path and name of the incoming json file.
    -o, --output [output]        Path and name of the resulting csv file. Defaults to console.
    -f, --fields <fields>        Specify the fields to convert.
    -l, --fieldList [list]       Specify a file with a list of fields to include. One field per line.
    -d, --delimiter [delimiter]  Specify a delimiter other than the default comma to use.
    -e, --eol [value]            Specify an EOL value after each row.
    -z, --newLine [value]        Specify an new line value for separating rows.
    -q, --quote [value]          Specify an alternate quote value.
    -n, --no-header              Disable the column name header
    -F, --flatten                Flatten nested objects
    -u, --unwindPath <paths>     Creates multiple rows from a single JSON document similar to MongoDB unwind.
    -L, --ldjson                 Treat the input as Line-Delimited JSON.
    -p, --pretty                 Use only when printing to console. Logs output in pretty tables.
    -a, --include-empty-rows     Includes empty rows in the resulting CSV output.
    -b, --with-bom               Includes BOM character at the beginning of the CSV.

An input file -i and fields -f are required. If no output -o is specified the result is logged to the console. Use -p to show the result in a beautiful table inside the console.

CLI examples

Input file and specify fields

$ json2csv -i input.json -f carModel,price,color

carModel,price,color
"Audi",10000,"blue"
"BMW",15000,"red"
"Mercedes",20000,"yellow"
"Porsche",30000,"green"

Input file, specify fields and use pretty logging

$ json2csv -i input.json -f carModel,price,color -p

Input file, specify fields and write to file

$ json2csv -i input.json -f carModel,price,color -o out.csv

Content of out.csv is

carModel,price,color
"Audi",10000,"blue"
"BMW",15000,"red"
"Mercedes",20000,"yellow"
"Porsche",30000,"green"

Input file, use field list and write to file

The file fieldList contains

carModel
price
color

Use the following command with the -l flag

$ json2csv -i input.json -l fieldList -o out.csv

Content of out.csv is

carModel,price,color
"Audi",10000,"blue"
"BMW",15000,"red"
"Mercedes",20000,"yellow"
"Porsche",30000,"green"

Read from stdin

$ json2csv -f price
[{"price":1000},{"price":2000}]

Hit Enter and afterwards CTRL + D to end reading from stdin. The terminal should show

price
1000
2000

Appending to existing CSV

Sometimes you want to add some additional rows with the same columns. This is how you can do that.

# Initial creation of csv with headings
$ json2csv -i test.json -f name,version > test.csv
# Append additional rows
$ json2csv -i test.json -f name,version --no-header >> test.csv

Include using a script tag (not recommended)

If it's not possible to work with node modules, json2csv can be declared as a global by requesting dist/json2csv.js via an HTML script tag:

<script src="node_modules/json2csv/dist/json2csv.js"></script>
<script>
  console.log(typeof json2csv === 'function'); // true
</script>

Building

When developing, it's necessary to run webpack to prepare the built script. This can be done easily with npm run build.

If webpack is not already available from the command line, use npm install -g webpack.

Testing

Run the following command to test and return coverage

$ npm test

Contributors

Install require packages for development run following command under json2csv dir.

Run

$ npm install

Could you please make sure code is formatted and test passed before submit Pull Requests?

See Testing section above.

But I want streams!

Check out my other module json2csv-stream. It transforms an incoming stream containing json data into an outgoing csv stream.

Similar Projects

• Papa Parse

License

See LICENSE.md.

Changelog

3.11.0 (2017-08-02)

Bug Fixes

• Handle dates without double-escaping (#189) (ff514ba)
• unwind parameter in command line mode (#191) (e706c25)

Features

• Added flag to signal if resulting function value should be stringified or not (#192) (aaa6b05)

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