compressed-json

String base JSON compressor

If you seriously want to reduce your data size, consider using msgpack.

Use compressed-json only if you cannot handle binary for some reason.

Install

npm i compressed-json

Usage

'use strict'

const cjson = require('compressed-json')

// Convert json object
const compressed = cjson.compress({ /* Large json */ })
const restored = cjson.decompress(compressed)

// Convert json string
const compressedString = cjson.compress.toString({ /* Some large json */ })
const restoredFromString = cjson.decompress.fromString(compressedString)

How It Works

compressed-json has two logics:

• Key-Compression
• String-Value-Pointing

Example compression

example-src.json

{
  "description": "This is example json",
  "entities": [
    {
      "id": 100,
      "name": "Dog",
      "desc": "This is desc of dog",
      "tag": ["animal"]
    },
    {
      "id": 101,
      "name": "Cat",
      "desc": "This is desc of cat",
      "tag": ["animal"]
    }
  ],
  "notes": [
    "Unique string will be kept as is",
    "Duplicated string will be combined",
    "Duplicated string will be combined",
    "p: string start with 'p:' will be escaped "
  ]
}

example-compressed.json

{
  "_": {
    "0": "This is example json",
    "1": [
      {
        "2": 100,
        "3": "Dog",
        "4": "This is desc of dog",
        "5": [
          "p:0"
        ]
      },
      {
        "2": 101,
        "3": "Cat",
        "4": "This is desc of cat",
        "5": [
          "p:0"
        ]
      }
    ],
    "6": [
      "Unique string will be kept as is",
      "p:1",
      "p:1",
      "e:p: string start with 'p:' will be escaped "
    ]
  },
  "K": [
    "description",
    "entities",
    "id",
    "name",
    "desc",
    "tag",
    "notes"
  ],
  "P": [
    "animal",
    "Duplicated string will be combined"
  ]
}

Structure of compressed json

| Key | Description | | --- | ----------- | | K | Array of original keys. Object keys are replaced with index of K in the compressed json | | P | Pointed string values. Values are replaced with index of P in the compressed json | | _ | Compressed payload. Keeps original structure, but keys and values may be replaced with pointers to K or P |

Key-Compression logic

All object keys are replaced with index of array stored in K of compressed JSON.

The more same key appears in original json, the more better compression.

String-Value-Pointing

String values appeared at least two will replaced with pointer string with contains index of array stored in P of compressed JSON.

The more same string value appears in original json, the more better compression.