The function jsonld2obj constructs an object graph in memory by resolving the @id properties recursively. The graph can contain cycles. This is handy if you want to navigate graphs represented in RDF (as json-ld) from javascript code.

Installation

# for yarn users
yarn add jsonld-object-graph

# for npm users
npm install jsonld-object-graph

Note: This library uses jsonld package as a dependency, which at some point depends on some native C code which needs to be compiled through gyp. Make sure you can compile native code on your platform. We build our package on Travis-CI, so you can take a look, how the build environment is configured (see .travis.yml file).

TL;DR

const data = ... get JSON-LD data from somewhere ...
const {jsonld2obj, autoSimplifier, mutateGraphKeys} = require("jsonld-object-graph")
const graph = await jsonld2obj(data)
mutateGraphKeys(autoSimplifier)(graph)

graph.Gordon.knows.Alyx.name // -> "Alyx Vence"
graph.Gordon.knows.Alyx.knows.name // -> "Gordon Freeman"

Example

const {jsonld2obj} = require("jsonld-object-graph")
const data = [
  {
    "@context": {
      "@base": "http://halflife/",
      "@vocab": "http://schema.org/",
      "knows": {
        "@type" :"@id"
      }
    },
    "@id": "Gordon",
    "@type": "Person",
    "gender": "male",
    "name": "Gordon Freeman",
    "knows": [
      {
        "@id": "Alyx",
        "@type": ["Person", "Hacker"],
        "gender": "female",
        "name": "Alyx Vence",
        "knows": "Gordon",
        "owns": "Pistol",
      },
      "Barney"
    ],
    "owns": ["Gravity Gun", "Crowbar"]
  }
]

const graph = await jsonld2obj(data)
console.log(graph)

Generates the following output:

{ 'http://halflife/Gordon':
   { 'http://halflife/Gordon': [Circular],
   ...
   ...
}

Now it is possible to navigate the graph as follows:

graph
  ["http://halflife/Alyx"]
  ["http://schema.org/knows"]
  ["http://schema.org/name"] // -> "Gordon Freeman"

graph
  ["http://halflife/Alyx"]
  ["http://schema.org/knows"]
  ["http://halflife/Gordon"]
  ["http://schema.org/name"] // -> "Gordon Freeman"

Shorteninig of property names

Of course, we don't like these huge identifiers in our code. To shorten the property names, such as http://schema.org/knows to knows, we can use the following function:

const {autoSimplifier, mutateGraphKeys} = require("jsonld-object-graph")
mutateGraphKeys(autoSimplifier)(graph) // mutates the graph in-place

Now it is possible to navigate the graph as follows:

graph.Gordon.knows.Alyx.name // -> "Alyx Vence"
graph.Gordon.knows.Alyx.knows.name // -> "Gordon Freeman"

The function mutateGraphKeys is not pure, it mutates the keys in the original graph. During this process, an exception is thrown if an ambigous replacement has occured.

Other replacement functions

• dropPrefix : removes prefix from each key
• dropNsPrefix : removes namespace prefix, e.g. schema:
• toUnderscores : replaces special characters to _ to make navigation in javascript easier
• afterLastSlash : keeps the word after the last slash e.g. http://schema.org/known to knows
• afterLastHash : e.g. http://something#abc to abc
• autoSimplifier : combines multiple operations

Replacements in a functional way

With ramda (or sanctuary) we can compose the replacements in a functional way as follows:

const {compose, replace} = require("ramda")
const replacers = compose(
  dropNsPrefix("foaf"),
  dropNsPrefix("schema"),
  replace(/...regex.../, "..."), // custom regex replacement
  /* ... */
)

Types resolved automagically

If your JSON-LD data contains the @type property, our function automatically resolves it into a javascript object and makes it accessible through $type property (for easier navigation in javascript)

graph.Gordon.$type // -> Multival(Person)
graph.Alyx.$type // -> Multival(Person, Hacker)

Configuration

Since v1.0.0, there is defaultConfig with sensible configuration parameters that can be customized as follows:

const { jsonld2objWithConfig, defaultConfig } = require("jsonld-object-graph")
const myConfig = { ...defaultConfig, addSelfRef:false }
const jsonld2obj = jsonld2objWithConfig(myConfig)

The following param can be configured:

• addSelfRef (default true) whether to add self-reference e.g. graph.Alyx.Alyx == graph.Alyx
• addTypeRef (default true) whether to add the resolved type object as an reference to its instance
• shouldResolveTypeObjects (default true) whether to resolve the "@type" as an object
• idFieldName (default "$id") how the "@id" field should be renamed
• typeFieldName (default "$type") how the "@type" field should be renamed