neoJSON

A data exchange & config format, a subset of ES2017, fully supporting JSON and JSON5 expressions, with added support for new expresssions.

// person.neojson.js
import { Person } from ".";
export default new Person({
  name: "John Doe",
  birthDate: new Date("1990-12-27"),
  roles: new Set(["admin", "moderator"]),
});

Why?

• You can statically typecheck your config files with TypeScript/Flow (by inferring the constructors' argument types).
• You can serialize and deserialize your own class instances.
• You can use Dates, RegExps, Sets and Maps.

Definition

Take JSON. Add comments, single quotes, unquoted keys, trailing commas and escaped newlines. That's roughly JSON5. Add new expressions, wrap it in an export default statement, and add the necessary import statements. That's neoJSON.

In a neoJSON file, the entire expression must be wrapped in export default:

export default {
  some: "JSON value",
};

You can use new expressions for some global classes:

export default {
  date: new Date("2022-12-27"),
  regexp: new RegExp("\\s+"),
  set: new Set(["admin", "moderator"]),
  map: new Map([[1, 2]]),
};

and you can use your own classes:

import MyClass from "./my-class.js";
import { MyPoint as Point } from "./my-point.js";
export default {
  x: new MyClass("hi"),
  y: new Point({ x: 1, y: 2 }),
};

Usage

import { parse, stringify } from "neojson";

class Person {
  constructor({ name, age }) {
    this.name = name;
    this.age = age;
  }
  toNeoJSON() {
    const { name, age } = this;
    return [{ name, age }]; // the constructor arguments
  }
}

// imports per file path
const imports = { ".": { Person } };

const person = new Person({ name: "Joe", age: 42 });
const str = stringify(person, { imports });
console.log(str);
console.log(parse(str, { imports }));

The generated neoJSON string is:

import { Person } from ".";
export default new Person({ name: "Joe", age: 42 });

API

parse(str, options)

Parses a neoJSON string and returns the value. options is an object with the following properties:

• imports (optional): an object mapping file paths to objects containing the constructors to use for new expressions. The default is {}.

stringify(value, options)

Stringifies a value to a neoJSON string. options is an object with the following properties:

• imports (optional): an object mapping file paths to objects containing the constructors to use for new expressions. The default is {}.

Is it safe?

As long as your constructors are safe and you don't provide the Function constructor to parse, yes. The parser does not use eval, it uses Babel's parser.