digitalbazaar
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 jsonldconst jsonld = require('jsonld');Browser (bundler) + npm
npm install jsonldUse your favorite bundling technology (webpack, Rollup, etc) to
directly bundle your code that loads jsonld. Note that you will need support
for ES2017+ code.
Browser Bundles
The built npm package includes bundled code suitable for use in browsers. Two versions are provided:
./dist/jsonld.min.js: A version built for wide compatibility with modern and older browsers. Includes many polyfills and code transformations and is larger and less efficient../dist/jsonld.esm.min.js: A version built for features available in browsers that support ES Modules. Fewer polyfills and transformations are required making the code smaller and more efficient.
The two bundles can be used at the same to to allow modern browsers to use
newer code. Lookup using script tags with type="module" and nomodule.
Also see the webpack.config.js if you would like to make a custom bundle for
specific targets.
Browser (AMD) + npm
npm install jsonldUse 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:jsonldimport * 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-nativeExamples
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-levelframe
// frame a document
const framed = await jsonld.frame(doc, frame);
// output transformed into a particular tree structure per the given framecanonize (normalize)
// canonize (normalize) a document using the RDF Dataset Canonicalization Algorithm
// (URDNA2015):
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-QuadsfromRDF (N-Quads)
// deserialize N-Quads (RDF) to JSON-LD
const doc = await jsonld.fromRDF(nquads, {format: 'application/n-quads'});
// doc is JSON-LDCustom 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});Node.js Document Loader User-Agent
It is recommended to set a default user-agent header for Node.js
applications. The default for the default Node.js document loader is
jsonld.js.
Safe Mode
A common use case is to avoid JSON-LD constructs that will result in lossy
behavior. The JSON-LD specifications have notes about when data is dropped.
This can be especially important when calling [canonize][] in order to
digitally sign data. A special "safe mode" is available that will detect these
situations and cause processing to fail.
Note: This mode is designed to be the common way that digital signing and similar applications use this library.
The safe options flag set to true enables this behavior:
// expand a document in safe mode
const expanded = await jsonld.expand(data, {safe: true});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/w3c/rdf-canonThey 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-suitesNode.js tests can be run with a simple command:
npm testIf you installed the test suites elsewhere, or wish to run other tests, use
the TESTS environment var:
TESTS="/tmp/org/test-suites /tmp/norm/tests" npm testThis feature can be used to run the older json-ld.org test suite:
TESTS=/tmp/json-ld.org/test-suite npm testBrowser testing can be done with Karma:
npm run test-karma
npm run test-karma -- --browsers Firefox,ChromeCode coverage of node tests can be generated in coverage/:
npm run coverageTo display a full coverage report on the console from coverage data:
npm run coverage-reportThe Mocha output reporter can be changed to min, dot, list, nyan, etc:
REPORTER=dot npm testRemote context tests are also available:
# run the context server in the background or another terminal
node tests/remote-context-server.js
TESTS=`pwd`/tests npm testTo 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 FirefoxTo generate an EARL report with the json-ld-api and json-ld-framing tests
as used on the official JSON-LD Processor Conformance page
TESTS="`pwd`/../json-ld-api/tests `pwd`/../json-ld-framing/tests" EARL="jsonld-js-earl.jsonld" npm testThe EARL .jsonld output can be converted to .ttl using the rdf tool:
rdf serialize jsonld-js-earl.jsonld --output-format turtle -o jsonld-js-earl.ttlOptionally follow the report instructions to generate the HTML report for inspection. Maintainers can submit updated results as needed.
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:
TESTS=/tmp/benchmark-manifest.jsonld BENCHMARK=1 npm testEARL reports with benchmark data can be generated with an optional environment details:
TESTS=`pwd`/../json-ld.org/benchmarks/b001-manifiest.jsonld BENCHMARK=1 EARL=earl-test.jsonld TEST_ENV=1 npm testSee tests/test.js for more TEST_ENV and BENCHMARK control and options.
These reports can be compared with the benchmarks/compare/ tool and at the
JSON-LD Benchmarks site.
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.
Source
The source code for the JavaScript implementation of the JSON-LD API is available at:
https://github.com/digitalbazaar/jsonld.js
Commercial Support
Commercial support for this library is available upon request from Digital Bazaar: support@digitalbazaar.com