node-appwrite/docs/examples/databases/create-relationship-attribute.md

Appwrite is an open-source self-hosted backend server that abstract and simplify complex and repetitive development tasks behind a very simple REST API

const sdk = require('node-appwrite');

const client = new sdk.Client()
    .setEndpoint('https://cloud.appwrite.io/v1') // Your API Endpoint
    .setProject('5df5acd0d48c2') // Your project ID
    .setKey('919c2d18fb5d4...a2ae413da83346ad2'); // Your secret API key

const databases = new sdk.Databases(client);

const result = await databases.createRelationshipAttribute(
    '<DATABASE_ID>', // databaseId
    '<COLLECTION_ID>', // collectionId
    '<RELATED_COLLECTION_ID>', // relatedCollectionId
    sdk.RelationshipType.OneToOne, // type
    false, // twoWay (optional)
    '', // key (optional)
    '', // twoWayKey (optional)
    sdk.RelationMutate.Cascade // onDelete (optional)
);