MongoDB Realm React Native SDK

import Realm from "realm";
const Cat = {
  name: "Cat",
  properties: {
    _id: "objectId",
    name: "string",
    age: "int",
    type: "string",
  },
};
// open a local realm with the 'Cat' schema
const realm = await Realm.open({
  schema: [Cat],
});

// retrieve the set of Cat objects
const cats = realm.objects("Cat");
console.log(`There are ${cats.length} cats`);
// filter for cats that are older than 7
const catsOlderThan7 = cats.filtered("age > 7");
console.log(
  `There are ${catsOlderThan7.length} cats older than 7 years old`
);
// filter for calico cats
const calicoCats = cats.filtered("type == 'Calico'");
console.log(`There are ${calicoCats.length} Calico cats`);

// find a cat named "Clover"
const cloverCat = cats.filtered("name == 'Clover'");
// update the Cat in a write transaction
realm.write(() => {
  // update clover's age to 5 years old
  cloverCat.age = 5;
}); // when the transaction completes, the cat's age is updated in the database
console.log(`Clover the cat is ${cloverCat.age} years old`);

// insert a cat into the database
let aliceCat;
realm.write(() => {
  aliceCat = realm.create("Cat", {
    _id: new BSON.ObjectID(),
    name: "Alice",
    age: 14,
    type: "Calico",
  });
});
// create a listener that logs new changes to the cat
aliceCat.addListener((obj, changes) => {
  changes.changedProperties.forEach((changedProperty) => {
    console.log(
      `${obj.name}'s ${changedProperty} was altered to be ${obj[changedProperty]}`
    ); // This should log "Alice's age was altered to be 15"
  });
});
// update the cat
realm.write(() => {
  aliceCat.age = 15;
});

// always access the latest data
const realmInstanceA = await Realm.open({
  schema: [Cat],
});
const realmInstanceB = await Realm.open({
  schema: [Cat],
});
// get a reference to a single cat object
// stored in the database from each realm instance
const calicoCatFromRealmInstanceA = realm
  .objects("Cat")
  .filtered("type = 'Calico'")[0];
const calicoCatFromRealmInstanceB = realm
  .objects("Cat")
  .filtered("type = 'Calico'")[0];
// update cat A's name
realm.write(() => {
  calicoCatFromRealmInstanceA.name = "Hestu";
});
// cat B instance automatically updates with the new name
expect(calicoCatFromRealmInstanceB.name).toBe("Hestu");

var config = {
  schema: [Cat], // predefined schema
  sync: {
    user: app.currentUser,
    partitionValue: "MyPartitionValue",
  },
};
// Open a realm with a configuration object that has a SyncConfiguration
// A SyncConfiguration requires both a logged-in user and a partition value
let realm = await Realm.open(config);
// start a write transaction
let darukCat;
realm.write(() => {
  // get a cat from the database to update
  darukCat = realm.objects("Cat").filtered("name = 'Daruk")[0];
  // change the cat's name
  darukCat.name = "Daruk Goron";
}); // when the transaction completes, the cat's name is updated in the database
// and synced to the connected Realm App