Added browser support

README.md

@@ -43,6 +43,8 @@ An open-source framework for building SPARQL query engines in Javascript/Typescr
 npm install --save sparql-engine
 ```
 
+We also provide a browser release under [browser/sparqlEngine.js](https://raw.githubusercontent.com/rdfjs/N3.js/main/browser/sparqlEngine.js). Check the browser folder for an example usage. Please note that it's still an experimental feature.
+
 # Getting started
 
 The `sparql-engine` framework allow you to build a custom SPARQL query engine on top of any data storage system.

browser/example.html

@@ -0,0 +1,109 @@
+
+<p id="out">
+  Found solutions: <br><br>
+</p>
+
+<script src="./N3.js"></script>
+<script src="./sparqlEngine.js"></script>
+<script>
+
+'use strict'
+
+const { Parser, Store } = N3
+const { HashMapDataset, Graph, PlanBuilder } = sparqlEngine
+
+// Format a triple pattern according to N3 API:
+// SPARQL variables must be replaced by `null` values
+function formatTriplePattern (triple) {
+  let subject = null
+  let predicate = null
+  let object = null
+  if (!triple.subject.startsWith('?')) {
+    subject = triple.subject
+  }
+  if (!triple.predicate.startsWith('?')) {
+    predicate = triple.predicate
+  }
+  if (!triple.object.startsWith('?')) {
+    object = triple.object
+  }
+  return { subject, predicate, object }
+}
+
+class N3Graph extends Graph {
+  constructor () {
+    super()
+    this._store = Store()
+  }
+
+  insert (triple) {
+    return new Promise((resolve, reject) => {
+      try {
+        this._store.addTriple(triple.subject, triple.predicate, triple.object)
+        resolve()
+      } catch (e) {
+        reject(e)
+      }
+    })
+  }
+
+  delete (triple) {
+    return new Promise((resolve, reject) => {
+      try {
+        this._store.removeTriple(triple.subject, triple.predicate, triple.object)
+        resolve()
+      } catch (e) {
+        reject(e)
+      }
+    })
+  }
+
+  find (triple) {
+    const { subject, predicate, object } = formatTriplePattern(triple)
+    return this._store.getTriples(subject, predicate, object)
+  }
+
+  estimateCardinality (triple) {
+    const { subject, predicate, object } = formatTriplePattern(triple)
+    return Promise.resolve(this._store.countTriples(subject, predicate, object))
+  }
+}
+
+const graph = new N3Graph()
+const dataset = new HashMapDataset('http://example.org#default', graph)
+
+// Load some RDF data into the graph
+const parser = new Parser()
+parser.parse(`
+  @prefix foaf: <http://xmlns.com/foaf/0.1/> .
+  @prefix : <http://example.org#> .
+  :a foaf:name "a" .
+  :b foaf:name "b" .
+`).forEach(t => {
+  graph._store.addTriple(t)
+})
+
+const query = `
+  PREFIX foaf: <http://xmlns.com/foaf/0.1/>
+  SELECT ?name
+  WHERE {
+    ?s foaf:name ?name .
+  }`
+
+// Creates a plan builder for the RDF dataset
+const builder = new PlanBuilder(dataset)
+
+// Get an iterator to evaluate the query
+const iterator = builder.build(query)
+
+// Read results
+iterator.subscribe(bindings => {
+  document.getElementById('out').innerText += JSON.stringify(bindings.toObject(), null, 2)
+}, err => {
+  console.error('error', err)
+}, () => {
+  console.log('Query evaluation complete!')
+})
+
+</script>
+