datamaker

A command-line Node.js script and library that generates JSON or CSV data in bulk. If you are building an IT system, then the chances are you'll need to populate a database (whether SQL or NoSQL) with some reasonably realistic data to test and benchmark with.

The datamaker tool allows sample data to be created by supplying:

• a template of how the data is to look. The data can contain multiple placeholders where sample data will be inserted e.g. {{firstname}},{{lastname}},{{date}}.
• the format of the output data: none, json or csv. This effects how the generated string data is processed prior to delivery.
• the number of records to be created.

Quick example:

$ echo "{{uuid}},{{date}},{{firstname}} {{surname}},{{email}}" | datamaker --format csv --iterations 5
10U9SHHE2463IH9E,1970-10-12,Marylee Dodge,[email protected]
379QYC80U5KYQP4D,1994-11-09,Melany Fuqua,[email protected]
DERC4Y2BQ6HCI0HI,1983-08-11,Cathleen Leal,[email protected]
00K8FEGZJO31Q08O,2005-06-18,Louie Lee,[email protected]
JDYSVPTAEXKEF9D8,1982-10-29,Dionne Vann,[email protected]

Pre-requisites

Node.js & npm are required to be pre-installed.

Installation

To install the command-line utility, use npm:

$ npm install -g datamaker

or add the library to an existing Node.js project:

$ npm install --save datamaker

Command-line parameters reference

• --template/-t - the path of the template file e.g --template /path/to/template.txt
• --format/-f - the target file format (none, csv, json or xml). Default none e.g. --format json
• --iterations/-i - the number of records to create. Default 1 e.g. --iterations 5000
• --list/-l - list the available tags

Generating CSV files

The template for a CSV file can be stored in a text file and supplied with the --template/-t parameter. Create a text file containing the following template:

{{uuid}},{{date}},{{time}},{{firstname}} {{surname}},{{street}},{{town}},{{zip}} {{statecode}},{{longitude}},{{latitude}}

The template contains the layout of each line of data, with placeholders for where the dynamic data is inserted. Save it as template.txt.

You may now run datamaker using this template:

$ datamaker -t ./template.txt -f csv -i 500

Alternatively, you can pipe in the template from elsewhere:

$ echo "{{uuid}},{{date}},{{firstname}} {{surname}},{{zip}}" | datamaker --format csv --iterations 10000 

Generating JSON data

JSON data is generated in a similar way. This time our template represents a single JSON document:

{
  "_id": "{{uuid}}",
  "name": "{{firstname}} {{surname}}",
  "occupation": "{{occupation}}",
  "religion": "{{religion}}",
  "dob": "{{date 2014-01-01}}",
  "status": "{{oneofl ok provisional rejected cancelled deleted}}",
  "accountType": "{{oneof bronze silver gold}}",
  "password": "{{password | sha256}}",
  "salt": "{{ words 5 | sha512}}",
  "lastIP": "{{ ip }}",
  "lastLogin": "{{date_iso 2020-01-01}}",
  "location": {
    "longitude": "{{ longitude NYC }}",
    "latitude": "{{ latitude NYC }}"
  },
  "address": {
    "street": "{{street}}",
    "town": "{{town}}",
    "postode": "{{postcode}}"
  },
  "telephone": "{{tel}}",
  "pets": ["{{cat}}","{{dog}}"],
  "email": "{{email true}}",
  "url": "{{website}}",
  "description": "{{words 20}}",
  "((loop children 4))":"{{firstname}}",
  "((loop friends 3))": {"name": "{{name}}", "email": "{{email}}"}
}

Save the template as template.json.

Run the datamaker as before but with json as the format parameter:

$ datamaker -t ./template.json -f json -i 500 
{"_id":"e87691f3232e493a8f7d5ed866bbf813","name":"Gertrude Ashcraft","occupation":"Television production assistant","religion":"Jeung San Do","dob":"2022-06-17","status":"cancelled","accountType":"silver","password":"6ae95ca5f8098007fc09f75761e85d4d1f6c9dc16e3f1679de4196127b0387b7","salt":"ccf2adf7bd7590eb2444c2ca0393805c534f60686c877b0a12c32dc645f9006d8ea3df9aeb0ebbeba941bb9cc54b3f6688b614ccfbcfa6954f86ba66fbec76e5","lastIP":"83.118.14.45","lastLogin":"2022-06-09T13:25:44.406Z","location":{"longitude":"-73.9759","latitude":"40.7312"},"address":{"street":"6681 Shipley","town":"Caister on Sea","postode":"RH5 7XD"},"telephone":"+597-4041-660-496","pets":["Rusty","Roxy"],"email":"[email protected]","url":"https://toronto.com","description":"bedding insertion advisory bunch terms manual language parameter gs jurisdiction experiment signing gratuit cheapest initiative kai proxy anniversary prescribed penetration","children":["Idalia","Allyson","Jadwiga","Luci"],"friends":[{"name":"Dalila Dunbar","email":"[email protected]"},{"name":"Tambra Caraway","email":"[email protected]"},{"name":"Cathleen Rivero","email":"[email protected]"}]}
...

Loops

Only in JSON-Templates you may use the loop-command to create an Array of data.

Usage:

"((loop property number[,max]))":{}

• property will be the name of the array
• number is the number of times to repeat the object into the resulting array. if used with a second number, a random number between these two will be used, eg. "((loop tags 2,9))": "{{word}}"

Example:

{
  "((loop items 2))": {
    "name":"{{word}}",
    "price":"{{price}}"
  }
}

results in

{
  "items": [
    {
      "name":"some",
      "price":"2.50"
    },
    {
      "name":"item",
      "price":"4.30"
    }
  ]
}

Note: to use the ((loop .. )) syntax, you must be using JSON mode (i.e. -f json and the template itself must parse as JSON correctly, which in practice means using no generated numbers or boolans).

Generating XML data

Create an XML template e.g. template.xml:

<?xml version="1.0"?>
<company>
  <name>{{company}}</name>
  <address>
    <street>{{street}}</street>
    <city>{{city}}</city>
    <state>{{state}}</state>
    <zip>{{statecode}}{{zip}}</zip>
  </address>
  <ceo>{{firstname}} {{surname}}</ceo>
  <dateCreated>{{date}}</dateCreated>
</company>

Run the datamaker as before but with xml as the format parameter:

$ datamaker -t ./template.xml -f xml -i 500 
<?xml version="1.0"?><company>  <name>Consulting </name>  <address>    <street>5270 Bispham Lane</street>    <city>Saint Louis</city>    <state>Alabama</state>    <zip>AZ83647</zip>  </address>  <ceo>Jefferey Harvey</ceo>  <dateCreated>2009-10-28</dateCreated></company>
...

Using datamaker to import data into Cloudant/CouchDB

Combining this tool with the couchimport utility allows data to be generated and imported into the a Cloudant/CouchDB database in one go:

$ datamaker -t ./template.json -f json -i 1000 | couchimport --db mydatabase
Reading data from stdin
written {"batch":1,"batchSize":500,"docSuccessCount":500,"docFailCount":0,"statusCodes":{"201":1},"errors":{}}
written {"batch":2,"batchSize":500,"docSuccessCount":1000,"docFailCount":0,"statusCodes":{"201":2},"errors":{}}
Import complete

The couchimport utility bundles the JSON into bulk API calls and posts them to the database via HTTP.

Filters

A datamaker tag can also include optional filters by supplying strings after a | character e.g.

$ echo '{{ name | toUpperCase }}' | datamaker
JANYCE MOE

Filters can be chained e.g.

$ echo '{{ words 5 | toUpperCase | toArray}}' | datamaker
["BUDAPEST","LICENSING","GMC","METHODOLOGY","MEM"]
$ echo '{{ name | toLowerCase | sha256 }}' | datamaker
76576efc53b4441d342acbca485457f948c1b97c4a2515a05ffc47aa524b5093

Available filters

• toUpperCase
• toLowerCase
• toTitleCase
• toArray
• md5
• sha1
• sha256
• sha512
• base64
• toString
• toBool
• toFloat
• toInt
• toObject
• encodeURIComponent
• escapeSingleQuotes - replaces single single quotes withe two single quotes, handy when generating SQL.
• escapeDoubleQuotes - replaces single double quotes with two double quotes.

Additionally for JSON formats, the following filters can be used within templates to output appropriate JSON datatypes:-

• toBool
• toFloat
• toInt
• toObject

As well as performing type conversion, these functions also "eat" up any double quotes around the host tag e.g.

{
  "alive": "{{boolean 0.75 | toBool}}",
  "count": "{{integer | toInt}}",
  "score": "{{float | toFloat}}"
}

returns:

{
  "alive": true,
  "count": 10,
  "score": 5.0
}

which is useful for making both the original template and the resultant object parse as valid JSON.

Tag reference

The Mustache-style tags you may use are listed below. Some tags allow extra parameters to be supplied to affect the range of random data generated

The code for the tags can be found in the plugins folder of the source code.

• A-E - addressuk addressus addressgerman airport autoinc boolean cat city cityGerman clf company country creditcard currency date date_iso digits dog domainname email emojii ethnicity
• F-O - file firstname float http_method http_path http_query_string http_reponse integer ip ip6 kuuid kuuidr last latitude letters longitude mac marque monarch name normal occupation oneof oneofl
• P-T - password president postcode price prime product religion sic state statecode street streetGerman surname tel time timestamp title tld town
• U-Z - unit url uuid uuidv4 walk website word words youtube zip

{{addressuk}}

Single-line UK address.

Parameters: none

e.g.

{{addressuk}} ---> 9315 Lancaster Circle, Haslingden, Nottinghamshire, HS15 6YD

{{addressus}}

Single-line US address.

Parameters: none

e.g.

{{addressus}} ---> 8184 Ambrose, Fontana, Minnesota, 44626

{{addressgerman}}

Single-line German address.

Parameters: none

e.g.

{{addressgerman}} ---> Bahnhofsstrasse 12, 80335 München

{{airport}}

Three-digit airport code.

Parameters: none

e.g.

{{airport}} ---> MTK

{{autoinc}}

Auto-incrementing number.

Parameters:

• starting number (default 1)

e.g.

{{autoinc 1000}} ---> 1000
{{autoinc}} ---> 1001

{{boolean}}

Boolean value.

Parameters:

• probability of being true (default 0.5)

e.g.

{{boolean}} ---> false
{{boolean 0.95}} ---> true

{{cat}}

Cat name.

Parameters: none

e.g.

{{cat}} ---> Smokey

{{city}}

US city name.

Parameters: none

e.g.

{{city}} ---> Fremont

{{cityGerman}}

German city name.

Parameters: none

e.g.

{{cityGerman}} ---> Berlin

{{clf}}

Log line in Common Logfile Format.

Parameters: none

e.g.

{{clf}} ---> 208.148.153.238 - lelah [29/Aug/2024:14:22:49 +0100] "GET /reel/hip.html HTTP/1.0" 200 71733

{{company}}

Company name.

Parameters: none

e.g.

{{company}} ---> Venusian Software Corp

{{country}}

Country name.

Parameters: none

e.g.

{{country}} ---> Lebanon

{{county}}

UK county name.

Parameters: none

e.g.

{{county}} ---> Derbyshire

{{creditcard}}

Credit card number.

Parameters: none

e.g.

{{creditcard}} ---> 6011867289904845

{{currency}}

Currency code.

Parameters: none

e.g.

{{currency}} ---> USD

{{date}}

Random date in YYYY-MM-DD format.

Parameters:

• min - minimum date or 'now' if the timestamp is to be the current date (default '1970-01-01')
• max - maximum date (default 'now')

e.g.

{{date}} ---> 1977-02-28
{{date 2015-01-01}} ---> 2018-08-02 // date after 2015-01-01
{{date 2015-01-01 2016-01-01}} ---> 2015-04-23 // date in 2015
{{date now}} ---> 2024-07-02 // the current date

{{date_iso}}

Random date in ISO-8601 format.

Parameters:

• min - minimum date or 'now' if the timestamp is to be the current date/time (default '1970-01-01')
• max - maximum date (default 'now')

e.g.

{{date_iso}} ---> 2013-05-24T02:44:04.687Z
{{date_iso 2015-01-01}} ---> 2018-07-09T22:15:30.512Z // date after 2015-01-01
{{date_iso 2015-01-01 2016-01-01}} ---> 2015-04-21T18:08:33.979Z // date in 2015
{{date_iso now}} ---> 2024-07-02T10:55:52.002Z // the current date

{{digits}}

String of numerals.

Parameters:

• numDigits (default 5)

e.g.

{{digits}} ---> 06984
{{digits 8}} ---> 61103920

{{dog}}

Dog name.

Parameters: none

e.g.

{{dog}} ---> Lucky

{{domainname}}

Domain name.

Parameters: none

e.g.

{{domainname}} ---> yallaer.com

{{email}}

Email address.

Parameters:

• whether to use the previous firstname/surname for the email generation

e.g.

{{email}} ---> [email protected]

# based on previous name
{{name}} ---> Sheba Arthur
{{email true}} ---> [email protected]

{{emojii}}

Emojii.

Parameters:

• numChars - number of characters (default 1)

e.g.

{{emojii}} ---> 👦
{{emojii 3}} ---> 🌹⛔💺

{{ethnicity}}

Ethnicity string.

Parameters: None

e.g.

{{ethnicity}} ---> Tuscan

{{file}}

Get a random line from a simple text-file, e.g.

line1
another line
yeah

Parameters:

• filename - full path to the file (no default)

e.g.

{{file /path/to/file.txt}} ---> line1

{{firstname}}

Human first name.

Parameters:

e.g.

{{firstname}} ---> Bethan

{{float}}

Floating point number.

Parameters:

• min (default 1)
• max (default 100)
• decimalPlaces (default 4)

e.g.

{{float}} ---> 13.8592
{{float 1000 2000 2}} ---> 1750.06

{{http_method}}

HTTP method. Either GET/PUT/POST/DELETE/HEAD/COPY, much more likely to be GET.

Parameters:

• n/a

e.g.

{{http_method}} ---> GET

{{http_path}}

HTTP path.

Parameters:

• n/a

e.g.

{{http_path}} ---> /curious/ranch/viruses.html?barriers=AJEAZDLK65QFHKZ1

{{http_query_string}}

An HTTP query string.

Parameters

• None

e.g.

{{http_query_string}} ---> ?offering=26&approaches=electricity&unsigned=sectors&actively=villa&adam=81ZVYDTDPXQTSK4J

{{http_response}}

HTTP response code. Either 200/400/401/403/302/500, much more likely to be 200.

Parameters:

• n/a

e.g.

{{http_response}} ---> 200

{{integer}}

Integer number.

Parameters:

• min (default 1)
• max (default 100)

e.g.

{{integer}} ---> 99
{{integer 1000 2000}} ---> 1523

{{ip}}

IP4 address.

Parameters:

• local - boolean (whether to generate an IP in the 192.168.1 range or not)

e.g.

{{ip}} ---> 63.235.50.110
{{ip true}} ---> 192.168.1.58

{{ip6}}

IP6 address.

Parameters:

• local - boolean (whether to generate an IP in the fc00::: range or not)

e.g.

{{ip6}} ---> 487d:375d:7bfe:b23b:d1e2:8934:cfb2:c17e
{{ip true}} ---> fc00:cefe:5dfc:14da:691d:b4bf:63ac:6d17

{{kuuid}}

Time-sortable, unique identifier. see here

Parameters:

• min (optional) - minimum date
• max (optional) - maximum date

e.g.

{{kuuid}} ---> 001g8LWk0Svk222Bd0Et0GeaBl1P1gkP
{{kuuid 2010-01-01 2019-01-01}} ---> 001eWhUE2HLix22HqmL5436NDm1p02X6

{{kuuidr}}

Time-sortable, unique identifier, but in reverse order. see here

Parameters:

• min (optional) - minimum date
• max (optional) - maximum date

e.g.

{{kuuidr}} ---> zzzwSGtT2o36oK17mC4R26dkHI1f1Xm0
{{kuuid 2010-01-01 2019-01-01}} ---> zzyTAKwG1uzH1N4Cl4xi1vZIE22oxrrT

{{last}}

The last generate value of the supplied tag. This is used to re-use generated data elsewhere in your template.

Parameters:

• tag - the name of the tag

e.g.

{{last uuid}} ---> HSFC5LQPCP84IVY7 (the last uuid that was generated by datamaker)

{{latitude}}

Decimal latitude.

Parameters:

• city - one of LON, NYC, TOK, SYD or PAR. If omitted a latitude anywhere in the world will by returned.

e.g.

{{latitude}} ---> -54.4371
{{latitude PAR}} ---> 48.8823

{{letters}}

String of uppercase characters.

Parameters:

• numLetters (default 5)

e.g.

{{letters}} ---> TVEHJ
{{letters 10}} ---> WOBOJRJFCU

{{longitude}}

Decimal longitude.

Parameters:

• city - one of LON, NYC, TOK, SYD or PAR. If omitted a longitude anywhere in the world will by returned.

e.g.

{{longitude}} ---> 175.2526
{{longitude PAR}} ---> 2.3815

{{mac}}

Mac address

Parameters: none

e.g.

{{mac}} ---> 23-0d-a3-3e-cf-d8

{{marque}}

Car manufacturer.

Parameters: none

e.g.

{{marque}} ---> Bugatti

{{monarch}}

King or Queen.

Parameters: none

e.g.

{{monarch}} ---> Henry VIII

{{occupation}}

Occupation string.

Parameters: none

e.g.

{{occupation}} ---> Midwife

{{oneof}}

Picks one of supplied values with an equal chance of each value appearing. See also oneofl.

Parameters: any number of strings

e.g.

{{oneof Gryffindor Hufflepuff Ravenclaw Slytherin}} ---> Slytherin

{{oneofl}}

Picks one of supplied values, items at the start of the list are much more likely to be returned. (the l in oneofl stands for "Log", as the Math.log10 function is used to get a non-linear probability of returning array items.)

Parameters: any number of strings

e.g.

{{oneofl complete new rejected cancelled }} ---> complete

Here's the distribution of results:

echo '{{oneofl a b c d e f g h i j k l m }}' | datamaker -i 10000 | sort | uniq -c
2692 a
1550 b
1097 c
 860 d
 675 e
 541 f
 465 g
 421 h
 388 i
 393 j
 317 k
 308 l
 293 m

{{name}}

Combination for firstname and surname. Equivalent of {{firstname}} {{surname}}.

Parameters: none

e.g.

{{name}} ---> Anna Flint

{{normal}}

Generates numbers on a normal distribution

Parameters:

• mean - centre of distribution (default 50)
• stddev - standard deviation (default 1)
• decimalPlaces - number of decimal places (default 4)

e.g.

{{normal}} ---> 50.1097
{{normal 20000 1000 2}} ---> 20370.88

{{password}}

A commonly-used password.

Parameters: none

e.g.

{{password}} ---> abcd1234
{{password | md5}} ---> 1f3870be274f6c49b3e31a0c6728957f

{{president}}

A US president

Parameters: None

e.g.

{{president}} ---> Richard Nixon

{{postcode}}

UK postcode.

Parameters: none

e.g.

{{postcode}} ---> KT4 0XS

{{price}}

Floating point price.

Parameters:

• min (default 1)
• max (default 100)

e.g.

{{price}} ---> 65.29
{{price 500 700}} ---> 521.98

{{prime}}

Prime number. If you supply impossible parameters, you will get 1 in reply.

Parameters:

• min (default 1)
• max (default 100)

e.g.

{{prime}} ---> 17
{{prime 1000 3000}} ---> 1657

{{product}}

Product name.

Parameters:

• None

e.g.

{{product}} ---> CARABAO
{{product | toTitleCase}} ---> Salt

{{religion}}

Religion

Parameters: none

e.g.

{{religion}} ---> Mandaean Nasaraean Sabeans

{{sic}}

Industry standard SIC code - business category

Parameters: none

e.g.

{{sic}} ---> Growing of tobacco

{{state}}

US state name.

Parameters: none

e.g.

{{state}} ---> Ohio

{{statecode}}

2-letter US state code.

Parameters: none

e.g.

{{statecode}} ---> NC

{{street}}

Street address.

Parameters: none

e.g.

{{street}} ---> 6502 Chantler Avenue

{{streetGerman}}

German Street name.

Parameters: none

e.g.

{{streetGerman}} ---> Schulstrasse

{{surname}}

Human surname.

Parameters: none

e.g.

{{surname}} ---> Doyle-Tyson

{{tel}}

International telephone number.

Parameters: none

e.g.

{{tel}} ---> +43-3040-100-474

{{time}}

Time in HH:MM:SS format.

Parameters: none

e.g.

{{time}} ---> 10:45:59

{{timestamp}}

Timestamp in milliseconds since 1970.

Parameters:

• min - minimum timestamp (default 0)
• max - maximum timestamp (default 'now')

e.g.

{{timestamp}} ---> 351543517819
{{timestamp 946684800000}} --> 1163308913102  // timestamp after 2000-01-01
{{timestamp 946684800000 978307200000}} --> 959753617250  // timestamp in year 2000

{{title}}

Honorific or title e.g. Mr, Mrs etc.

Parameters: none

e.g.

{{title}} ---> Reverend

{{tld}}

Top level domain, or common domain name ending.

Parameters: none

e.g.

{{tld}} ---> gov.pr

{{town}}

UK town name.

Parameters: none

e.g.

{{town}} ---> Dudley

{{unit}}

An SI Unit

Parameters: none

e.g.

{{unit}} ---> °C

{{url}}

Full URL.

Parameters: none

e.g.

{{url}} ---> https://www.jovinianist.com/microcosmology.html?adrenalone=VEF0TSB23N04V8MO

{{uuid}}

Unique identifier.

Parameters: none

e.g.

{{uuid}} ---> C3QTU8YIVKZY126Q

{{uuidv4}}

Unique identifier v4.

Parameters: none

e.g.

{{uuidv4}} ---> d1e606b0-0452-46a7-9190-8671a82fdea0

{{ walk }}

Random walk. A single floating point number that "walks" in value between invocations.

Parameters:

• start - the start value (Default: 0)
• inc - the max increment (Default: 1)
• places - the number of decimal places in the output (Default: 4)
• ref - a reference for this value, so that multiple "walk" tags can be used in the same datamaker template (Default: ref)

e.g.

{{walk}} ---> -0.4405
{{walk 50 0.5 6 x}} ---> 50.099534
{{walk -1.1 0.2 6 y}} ---> -1.163953
{{walk 50 0.5 6 x}} ---> 50.311757
{{walk -1.1 0.2 6 y}} ---> -0.965426

{{website}}

Full website URL.

Parameters: none

e.g.

{{website}} ---> http://unlyrically.com

{{word}}

Single word.

Parameters: none

e.g.

{{word}} ---> synentognathous

{{words}}

Multiple words.

Parameters:

• count (default 5)

e.g.

{{words}} ---> piacularly burp archisymbolical glumaceous Calinago
{{words 2}} --->Xenomorpha mauler

{{youtube}}

Random YouTube URL.

Parameters: none

e.g.

{{youtube}} ---> https://www.youtube.com/watch?v=dQw4w9WgXcQ

{{zip}}

US ZIP code.

Parameters: none

e.g.

{{zip}} ---> 69882

Using as a library

You can use this npm module as a library in your own code

let dg = require('datamaker')
const template = '{{title}} {{firstname}} {{surname}}'
const format = 'none'
const iterations = 500
dg.generate(template, format, iterations)
  .on('data', (d) => { console.log(d) })
  .on('end', (d) => { console.error('Done!') })

or there are helper functions that return Promises e.g.

// get a single item
await dg.single('{{uuid}},{{name}}', 'csv')
// get a batch of 50 items
await dg.batch('{"name": "{{name}}","email": "{{email}}"}', 'json', 50)

Custom Plugins

When using datamaker as a library it is possible to extend its capability by defining custom plugins to suit the individual needs of a project. A custom plugin should be located inside the /datamaker/plugins/ folder at the root of the applications project with each plugin created as a separate js file within a namespace folder allowing plugins to referenced in templates as {{namespace:plugin}}. For example:

datamaker
└── plugins
    └── myorg
        └── employeeid.js

With the custom employeeid plugin defined as follows:

module.exports = () => {
  const min = 1000000
  const max = 3000000
  return (Math.floor(min + Math.random() * (max - min))).toString()
}

The custom plugin can then be referenced in a template using {{myorg:employeeid}} as follows:

let dg = require('datamaker')
const template = '{{myorg:employeeid}} {{title}} {{firstname}} {{surname}}'
const format = 'none'
const iterations = 5
dg.generate(template, format, iterations)
  .on('data', (d) => { console.log(d) })
  .on('end', (d) => { console.error('Done!') })

Resulting in the following:

2286807 Mr Athena Bowles
1727729 Prof Heidi Barrow
2411511 Mr Lawanna Karr
2898717 Mrs Londa Wingate
1756263 Ms Lashay Pitre

Formatting

The --format/-f parameter defines

• how the text in each substition is pre-processed before output e.g. in json mode double quotes are escaped correctly.
• how each line of output is processed prior to output e.g. in json mode the completed template is parsed to check it is valid JSON before being output on a a single line followed by a \n character

The code for the formatters can be found in the formatters folder of the source code.

A note on the data

The data generated by this tool is biased towards UK and US data sets. The names, towns, streets and postcodes are gleaned from western data sets. If you need data that resembles a different geography or contains more challenging character sets, then the feel free to fork the code and modify the stock data from the plugins folder or follow the guidance above and add your own specific custom plugins.

Note that generating an address with {{street}},{{city}},{{state}},{{statecode}}{{zip}} will generate that appears at a glance to be a reasonble address, but is patently nonsense:

$ echo "{{street}},{{city}},{{state}},{{statecode}}{{zip}}" | datamaker
6682 Crowcroft Circle,Nashua,New York,UT00769

The plugins do not coordinate with each other to ensure that the street exists in the city, or that the city exists in the state, or that the state code matches the state. That would require a more sophisticated and much larger data set!

Also note that the email addresses, zip codes, domain names, telephone numbers, websites and postcodes are fabricated. Airports, towns, states, state codes, cities, counties, countries and currencies are real.