JSONR - JSON with Refs

JSONR is the JSON serialization language plus refs.

"What is refs?" You might ask.

A ref allows the same object to be referenced multiple times within a file, so that referential equality will be preserved by the serialization. The syntax of refs follow the refs feature in YAML.

Install

npm install @airportyh/jsonr

Example

Let's say you want to model a family of people and the relationships between them.

const dad = { name: "Toby" };
const mom = { name: "Wendy" };
dad.spouse = mom;
mom.spouse = dad;

const marty = { name: "Marty" };
const linus = { name: "Linus" };
const emma = { name: "Emma" };

const children = [
    marty, linus, emma
];

dad.children = children;
mom.children = children;

for (let child of children) {
    child.father = dad;
    child.mother = mom;
}

marty.siblings = [linus, emma];
linus.siblings = [marty, emma];
emma.siblings = [linus, marty];

const family = {
    mom, dad, marty, linus, emma
};

You shall note that if you traverse the object graph starting at the variable family, you will encounter the same objects multiple times. For example, marty can be reached by any of the following: family.marty, family.dad.children[0], family.linus.siblings[0].

If we try to serialize this object graph using JSON.stringify(family), you'll get a

TypeError: Converting circular structure to JSON

But if you do it with JSONR:

const jsonr = require("@airportyh/jsonr");
console.log(jsonr.stringify(family, "  "));

You get (output):

{
  "mom": &1 {
    "name": "Wendy",
    "spouse": &2 {
      "name": "Toby",
      "spouse": *1,
      "children": &3 [
        &4 {
          "name": "Marty",
          "father": *2,
          "mother": *1,
          "siblings": [
            &5 {
              "name": "Linus",
              "father": *2,
              "mother": *1,
              "siblings": [
                *4,
                &6 {
                  "name": "Emma",
                  "father": *2,
                  "mother": *1,
                  "siblings": [
                    *5,
                    *4
                  ]
                }
              ]
            },
            *6
          ]
        },
        *5,
        *6
      ]
    },
    "children": *3
  },
  "dad": *2,
  "marty": *4,
  "linus": *5,
  "emma": *6
}

The &<NUMBER> tag (ex. &1) defines the ref ID of an object or array which follows that tag. The *<NUMBER> syntax (ex. *1) refers the the object that was defined with the given ref ID.

In this JSONR output, dad was given the ref ID of 2, mom was given 1, marty was given 4, linus 5, and emma 6. The children array which was shared by mom and dad was given the ref ID of 3.

Another benefit of refs, other than allowing the serialization of objects graphs with circular references, is the saving of file size when there exists shared references. One application of this concept is the serialization of immutable data structures which make heavy use of structural sharing.

API

JSONR, like JSON has 2 API methods:

• parse(jsonrString) - takes a JSONR string, and returns a JavaScript data structure
• stringify(data, indent) - takes a JavaScript data structure, a string representing indentation amount such as a tab or 2 spaces, and returns a string in JSONR format.

Todo

• load tests
• learn about the Lempel-Ziv-Welch algorithm and maybe use it instead
• add refs for strings?
• maybe rewrite _stringify
• publish to npm (done)
• clean up code (done)
• add data deserialization to parser (done)
• Investigate weird performance bug (done)
• implement ref feature to parser (done)
• add serializer(done)
• fix bug with family round trip (done)
• top level jsonr.js file (done)
• documentation (done)
• use family as example (done)
• fix the family round trip props getting re-ordered (done)