jsonld.js
Introduction
This library is an implementation of the JSON-LD specification in
JavaScript.
JSON, as specified in RFC7159, is a simple language for representing
objects on the Web. Linked Data is a way of describing content across
different documents or Web sites. Web resources are described using
IRIs, and typically are dereferencable entities that may be used to find
more information, creating a "Web of Knowledge". JSON-LD is intended
to be a simple publishing method for expressing not only Linked Data in
JSON, but for adding semantics to existing JSON.
JSON-LD is designed as a light-weight syntax that can be used to express
Linked Data. It is primarily intended to be a way to express Linked Data
in JavaScript and other Web-based programming environments. It is also
useful when building interoperable Web Services and when storing Linked
Data in JSON-based document storage engines. It is practical and
designed to be as simple as possible, utilizing the large number of JSON
parsers and existing code that is in use today. It is designed to be
able to express key-value pairs, RDF data, RDFa data,
Microformats data, and Microdata. That is, it supports every
major Web-based structured data model in use today.
The syntax does not require many applications to change their JSON, but
easily add meaning by adding context in a way that is either in-band or
out-of-band. The syntax is designed to not disturb already deployed
systems running on JSON, but provide a smooth migration path from JSON
to JSON with added semantics. Finally, the format is intended to be fast
to parse, fast to generate, stream-based and document-based processing
compatible, and require a very small memory footprint in order to operate.
Conformance
This library aims to conform with the following:
- JSON-LD 1.0,
W3C Recommendation,
2014-01-16, and any errata - JSON-LD 1.0 Processing Algorithms and API,
W3C Recommendation,
2014-01-16, and any errata - JSON-LD 1.0 Framing,
Unofficial Draft,
2012-08-30 - JSON-LD 1.1,
Draft Community Group Report,
2018-06-07 or newer - JSON-LD 1.1 Processing Algorithms and API,
Draft Community Group Report,
2018-06-07 or newer - JSON-LD 1.1 Framing,
Draft Community Group Report,
2018-06-07 or newer - Community Group test suite
The JSON-LD Working Group is now developing JSON-LD 1.1. Library
updates to conform with newer specifications will happen as features stabilize
and development time and resources permit.
- JSON-LD 1.1,
W3C Working Draft,
2018-12-14 or newer - JSON-LD 1.1 Processing Algorithms and API,
W3C Working Draft,
2018-12-14 or newer - JSON-LD 1.1 Framing,
W3C Working Draft,
2018-12-14 or newer - Working Group test suite
The test runner is often updated to note or skip newer tests that are not
yet supported.
Installation
node.js + npm
npm install jsonld
const jsonld = require('jsonld');
Browser (AMD) + npm
npm install jsonld
Use your favorite technology to load node_modules/dist/jsonld.min.js.
CDNJS CDN
To use CDNJS include this script tag:
<script src="https://cdnjs.cloudflare.com/ajax/libs/jsonld/1.0.0/jsonld.min.js"></script>
Check https://cdnjs.com/libraries/jsonld for the latest available version.
jsDeliver CDN
To use jsDeliver include this script tag:
<script src="https://cdn.jsdelivr.net/npm/jsonld@1.0.0/dist/jsonld.min.js"></script>
See https://www.jsdelivr.com/package/npm/jsonld for the latest available version.
unpkg CDN
To use unpkg include this script tag:
<script src="https://unpkg.com/jsonld@1.0.0/dist/jsonld.min.js"></script>
See https://unpkg.com/jsonld/ for the latest available version.
JSPM
jspm install npm:jsonld
import * as jsonld from 'jsonld';
// or
import {promises} from 'jsonld';
// or
import {JsonLdProcessor} from 'jsonld';
node.js native canonize bindings
For specialized use cases there is an optional rdf-canonize-native package
available which provides a native implementation for canonize(). It is used
by installing the package and setting the useNative option of canonize() to
true. Before using this mode it is highly recommended to run benchmarks
since the JavaScript implementation is often faster and the bindings add
toolchain complexity.
npm install jsonld
npm install rdf-canonize-native
Examples
Example data and context used throughout examples below:
const doc = {
"http://schema.org/name": "Manu Sporny",
"http://schema.org/url": {"@id": "http://manu.sporny.org/"},
"http://schema.org/image": {"@id": "http://manu.sporny.org/images/manu.png"}
};
const context = {
"name": "http://schema.org/name",
"homepage": {"@id": "http://schema.org/url", "@type": "@id"},
"image": {"@id": "http://schema.org/image", "@type": "@id"}
};
compact
// compact a document according to a particular context
const compacted = await jsonld.compact(doc, context);
console.log(JSON.stringify(compacted, null, 2));
/* Output:
{
"@context": {...},
"name": "Manu Sporny",
"homepage": "http://manu.sporny.org/",
"image": "http://manu.sporny.org/images/manu.png"
}
*/
// compact using URLs
const compacted = await jsonld.compact(
'http://example.org/doc', 'http://example.org/context', ...);
expand
// expand a document, removing its context
const expanded = await jsonld.expand(compacted);
/* Output:
{
"http://schema.org/name": [{"@value": "Manu Sporny"}],
"http://schema.org/url": [{"@id": "http://manu.sporny.org/"}],
"http://schema.org/image": [{"@id": "http://manu.sporny.org/images/manu.png"}]
}
*/
// expand using URLs
const expanded = await jsonld.expand('http://example.org/doc', ...);
flatten
// flatten a document
const flattened = await jsonld.flatten(doc);
// output has all deep-level trees flattened to the top-level
frame
// frame a document
const framed = await jsonld.frame(doc, frame);
// output transformed into a particular tree structure per the given frame
canonize (normalize)
// canonize (normalize) a document using the RDF Dataset Normalization Algorithm
// (URDNA2015), see:
const canonized = await jsonld.canonize(doc, {
algorithm: 'URDNA2015',
format: 'application/n-quads'
});
// canonized is a string that is a canonical representation of the document
// that can be used for hashing, comparison, etc.
toRDF (N-Quads)
// serialize a document to N-Quads (RDF)
const nquads = await jsonld.toRDF(doc, {format: 'application/n-quads'});
// nquads is a string of N-Quads
fromRDF (N-Quads)
// deserialize N-Quads (RDF) to JSON-LD
const doc = await jsonld.fromRDF(nquads, {format: 'application/n-quads'});
// doc is JSON-LD
Custom RDF Parser
// register a custom synchronous RDF parser
jsonld.registerRDFParser(contentType, input => {
// parse input to a jsonld.js RDF dataset object... and return it
return dataset;
});
// register a custom promise-based RDF parser
jsonld.registerRDFParser(contentType, async input => {
// parse input into a jsonld.js RDF dataset object...
return new Promise(...);
});
Custom Document Loader
// how to override the default document loader with a custom one -- for
// example, one that uses pre-loaded contexts:
// define a mapping of context URL => context doc
const CONTEXTS = {
"http://example.com": {
"@context": ...
}, ...
};
// grab the built-in node.js doc loader
const nodeDocumentLoader = jsonld.documentLoaders.node();
// or grab the XHR one: jsonld.documentLoaders.xhr()
// change the default document loader
const customLoader = async (url, options) => {
if(url in CONTEXTS) {
return {
contextUrl: null, // this is for a context via a link header
document: CONTEXTS[url], // this is the actual document that was loaded
documentUrl: url // this is the actual context URL after redirects
};
}
// call the default documentLoader
return nodeDocumentLoader(url);
};
jsonld.documentLoader = customLoader;
// alternatively, pass the custom loader for just a specific call:
const compacted = await jsonld.compact(
doc, context, {documentLoader: customLoader});
Related Modules
- jsonld-cli: A command line interface tool called
jsonldthat exposes
most of the basic jsonld.js API. - jsonld-request: A module that can read data from stdin, URLs, and files
and in various formats and return JSON-LD.
Commercial Support
Commercial support for this library is available upon request from
Digital Bazaar: support@digitalbazaar.com
Source
The source code for the JavaScript implementation of the JSON-LD API
is available at:
http://github.com/digitalbazaar/jsonld.js
Tests
This library includes a sample testing utility which may be used to verify
that changes to the processor maintain the correct output.
The main test suites are included in external repositories. Check out each of
the following:
https://github.com/w3c/json-ld-api
https://github.com/w3c/json-ld-framing
https://github.com/json-ld/json-ld.org
https://github.com/json-ld/normalization
They should be sibling directories of the jsonld.js directory or in a
test-suites dir. To clone shallow copies into the test-suites dir you can
use the following:
npm run fetch-test-suites
Node.js tests can be run with a simple command:
npm test
If you installed the test suites elsewhere, or wish to run other tests, use
the JSONLD_TESTS environment var:
JSONLD_TESTS="/tmp/org/test-suites /tmp/norm/tests" npm test
This feature can be used to run the older json-ld.org test suite:
JSONLD_TESTS=/tmp/json-ld.org/test-suite npm test
Browser testing can be done with Karma:
npm run test-karma
npm run test-karma -- --browsers Firefox,Chrome
Code coverage of node tests can be generated in coverage/:
npm run coverage
To display a full coverage report on the console from coverage data:
npm run coverage-report
The Mocha output reporter can be changed to min, dot, list, nyan, etc:
REPORTER=dot npm test
Remote context tests are also available:
# run the context server in the background or another terminal
node tests/remote-context-server.js
JSONLD_TESTS=`pwd`/tests npm test
To generate earl reports:
# generate the earl report for node.js
EARL=earl-node.jsonld npm test
# generate the earl report for the browser
EARL=earl-firefox.jsonld npm run test-karma -- --browser Firefox
Benchmarks
Benchmarks can be created from any manifest that the test system supports.
Use a command line with a test suite and a benchmark flag:
JSONLD_TESTS=/tmp/benchmark-manifest.jsonld JSONLD_BENCHMARK=1 npm test
