JavaScript quick start
At the end of this guide, you will have created a JavaScript program that connects to the Memgraph database and executes simple queries.
Running queries directly from a web browser is not recommended because of additional requirements and possible performance issues. In other words, we encourage you to use server-side libraries and clients for top performance whenever possible.
Prerequisites
To follow this guide, you will need:
- A running Memgraph instance. If you need to set up Memgraph, take a look at the Installation guide.
- A basic understanding of graph databases and the property graph model.
Basic Setup
Let's jump in and connect a simple program to Memgraph.
1. Create a new directory for your application, for example /MyApp and
position yourself in it.
2. To make the actual program, create a program.html file and add the
following code:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>Javascript Browser Example | Memgraph</title>
<script src="https://cdn.jsdelivr.net/npm/neo4j-driver"></script>
</head>
<body>
<p>Check console for Cypher query outputs...</p>
<script>
const driver = neo4j.driver(
"bolt://localhost:7687",
neo4j.auth.basic("", "")
);
(async function main() {
const session = driver.session();
try {
await session.run("MATCH (n) DETACH DELETE n;");
console.log("Database cleared.");
await session.run("CREATE (alice:Person {name: 'Alice', age: 22});");
console.log("Record created.");
const result = await session.run("MATCH (n) RETURN n;");
console.log("Record matched.");
const alice = result.records[0].get("n");
const label = alice.labels[0];
const name = alice.properties["name"];
const age = alice.properties["age"];
if (label != "Person" || name != "Alice" || age != 22) {
console.error("Data doesn't match.");
}
console.log("Label: " + label);
console.log("Name: " + name);
console.log("Age: " + age);
} catch (error) {
console.error(error);
} finally {
session.close();
}
driver.close();
})();
</script>
</body>
</html>
3. Open the program.html file in your browser and look for the output in
the console.
You should see an output similar to the following:
Database cleared.
Record created.
Record matched.
Label: Person
Name: Alice
Age: 22
Transaction timeout
Both automatic transactions and explicit transactions can be provided with a timeout.
Automatic transaction
const session: RxSession = driver.rxSession({ defaultAccessMode: 'READ' });
session
.run("MATCH (), (), (), () RETURN 42 AS thing;", // NOTE: A long query
undefined,
{ timeout: 50 } // NOTE: with a short timeout
)
.records()
.pipe(finalize(() => {
session.close();
driver.close();
}))
.subscribe({
next: record => { },
complete: () => { console.info('complete'); process.exit(1); }, // UNEXPECTED
error: msg => console.error('Error:', msg.message), // NOTE: expected to error with server side timeout
});
Explicit transaction
const session = driver.rxSession({ defaultAccessMode: 'READ' });
session
.beginTransaction({ timeout: 50 }) // NOTE: a short timeout
.pipe(
mergeMap(tx =>
tx
.run('MATCH (),(),(),() RETURN 42 AS thing;') // NOTE: a long query
.records()
.pipe(
catchError(err => { tx.rollback(); throw err; }),
concatWith(EMPTY.pipe(finalize(() => tx.commit())))
)
),
finalize(() => { session.close(); driver.close() })
)
.subscribe({
next: record => { },
complete: () => { console.info('complete'); process.exit(1); }, // UNEXPECTED
error: msg => console.error('Error:', msg.message), // NOTE: expected to error with server side timeout
})
Where to next?
For real-world examples of how to use Memgraph, we suggest you take a look at the Tutorials page. You can also browse through the How-to guides section to get an overview of all the functionalities Memgraph offers.