Short introduction into Realm for JavaScript developers

1. Kenneth Geisshirt
Building mobile apps with Realm for React Native
kgeisshirt

2. What is Realm JavaScript?
Provides an API for schema creation, object creation, transactions,
and queries
Try to be true to the spirit of JavaScript as possible
Realm objects act like JavaScript objects but they are live
(observable) objects

3. What is supported?
React Native
§ Android (32 and 64 bit)
§ iOS (requires Xcode 9+)
Node.js v8 and v10
§ Windows 8+, Linux and MacOS
§ v12 is planned for late summer
TypeScript definitions included
Electron is not officially supported (but works)

4. Where does it fit in?
Realm can be a local-only database
§ Store and query objects locally
Realm can be synced with a backend
§ Share data between devices
§ Work offline and resume syncing when connectivity is
restored
In progress (no ETA): sync your local Realm with MongoDB

5. export const Project = {
name: "Project",
primaryKey: "projectId",
properties: {
projectId: "string",
owner: "string",
name: "string",
timestamp: "date",
items: "Item[]"
}
};
Define a data model
export const Item = {
name: "Item",
primaryKey: "itemId",
properties: {
itemId: "string",
body: "string",
isDone: "bool",
timestamp: "date"
}
};

6. const creds = Realm.Sync.Credentials.usernamePassword('johndoe',
's3crEt');
const user = await Realm.Sync.User.login('http://my-realm-
server.example.com:9080', creds);
const config = user.createConfiguration({
schema: [Project, Item]
});
const realm = await Realm.open(config);
Logging in and open a Realm

7. realm.write(() => {
realm.create('Project', {
projectId: uuid(),
owner: Realm.Sync.User.current.identity,
name: 'MongoDB World’,
timestamp: new Date(),
});
});
Create an object

8. myProjects = realm
.objects('Project’)
.filtered('owner == $0', user.identity)
.sorted('timestamp', true);
activeProjects = realm
.objects('Project’)
.filtered('items.@count > 0');
Queries made easy

9. projects.addListener((collection, changes) => {
// changes.insertions
// changes.modifications
// changes.deletions
updateUI(changes);
});
Observable (live) objects - notifications

10. Links and stuff
Bug reports and source code: https://github.com/realm/realm-
javascript
General documentation: https://realm.io
JS specific documentation: https://realm.io/docs/javascript/latest/
API documentation: https://realm.io/docs/javascript/latest/api/
Try a demo app: https://github.com/realm/my-first-realm-app