1.0.0 • Public • Published


Working with static JSON files for mocking data or whatever other purposes can be a real bore. Jazzon is a convenience utility for generating, concatenating and streamlining the handling of static JSON files.


$ npm install --save jazzon


In and of it self jazzon does nothing, really. It's sole purpose is to call registered plugins with the current state and identified helpers. Helpers can be chained passing the current state from one to the next.

To illustrate a most basic scenario, this is how one might use jazzon together with jazzon-uuid

const jazzon = require('jazzon');
const uuid = require('jazzon-uuid');
let data = { id: "@{ uuid }" };
  .then(result => console.log(result)); // => {id: "6c84fb90-12c4-11e1-840d-7b25c5ee775a"}

In this scenario, jazzon encounters the helper uuid and calls each registered plugin (in this case jazzon-uuid) on it.

Helpers can also be chained using the pipe (|) symbol. Each chained helper gets the output (state) of the previous helper to operate on. To illustrate a more complex scenario, take these two models:

// user.json
  "id": "@{ uuid }",
  "name": "@{ name.findName }",
  "email": "@{ internet.email }",
  "username": "@{ internet.userName }"
// users.json
  "total": 3,
  "users": "@{ import(user.json) | pick(id, username) | repeat(3) }"

Running users.json through jazzon would produce something like this:

  "total": 3,
  "users": [{
    "id": "a76f535f-cbc6-4c09-8151-573e200c1dbf",
    "username": "Doug.Simonis28"
  }, {
    "id": "0a512648-c418-40a6-90ac-1bb5ef1e7fab",
    "username": "Virgil_Kunze"
  }, {
    "id": "88d6903f-d13b-4d16-877e-f906461c69aa",
    "username": "Grady.Koelpin"


The syntax of helpers are very similar to JavaScript template strings to clearly illustrate their purpose. But do not confuse them as the pipe separator is not a valid JavaScript operator.

The string must start with @{ and end with }. Each helper is separated with a | symbol. Encountering an invalid template-ish string will throw an error.

Use this regexr to experiment with the template strings.


Plugins should export a function that get's called once for every helper encountered by jazzon. The convention is to export a factory function that returns the plugin.

A plugin really is just a reducer that jazzon uses to process all the helpers. Therefore a plugin should always return a state, even if it does not manipulate the state. A switch statement does the job as so:

// myplugin.js
module.exports = function (otions) {
  return function (state, helper, args) {
    switch (helper) {
    case 'name':
      return args[0] || options.default;
    case 'wrap':
      return `Hello ${ state }!`;
      return state;
// myprogram.js
    default: 'world'
    "first": "@{ name | wrap }",
    "second": "@{ name(Joe) | wrap }"
  .then(result => console.log(result)); // => {"first": "Hello world!", "second": "Hello Joe!"}

Jazzon also supports async plugins. Under the hood, jazzon is using co so anything that co can handle, jazzon can handle. As so, other than just plain strings, a plugin may return a Promise, generator, generator function, function, object or array. Due to the awesome nature of co, objects and arrays may contain nestled objects/arrays containing Promises or any of the other supported types. See some of the plugins for examples of how this is achieved.

Availible plugins

To add your own plugin, add it to the list and make a pull request.


  • jazon.create(/*plugins*/) Creates a new instance of jazzon with optional list of plugins.
    • Returns jazzon
  • jazzon.use(plugin) Adds a plugin to be used when transforming template strings.
    • Returns jazzon
  • jazzon.compile(object) Iterates over the object looking for template strings to transform.
    • Returns a Promise
  • jazzon.plugins An list of registered helpers on this instance.
    • Returns an Array
    • Is immutable


  • Add documentation
  • Add wrapper for non-Promises returned from plugins
  • Add test for plugins (generator/non-generator)
  • Better error handling
  • Add CLI


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