PouchDB Subscription Events

Node module that emits PouchDB database changes as events. The module allows subscription to live changes.

Options

• find: if a selector is set, use the pouchdb-find module
• selector: condition to pass to pouchdb-find

In subscribe():

• since: database sequence to start at (default = 0)

Examples

import PouchDB from "pouchdb";
import PouchDBSubscription from "pouchdb-subscription";
import PouchDBAdapterMemory from "pouchdb-adapter-memory";
import PouchDBFind from "pouchdb-find";

PouchDB.plugin(PouchDBAdapterMemory);
PouchDB.plugin(PouchDBFind);

const db = new PouchDB('employees', {adapter: 'memory'});

await db.createIndex({
	index: {
		fields: ['department']
	}
});

const subscriptionMaster = new PouchDBSubscription(db, {
    find: true,
    selector: {department: 'Engineering'}
});

subscriptionMaster.on('subscriptions', subscriptions => {
	console.log("Number of subscriptions", subscriptions);
	// maybe when subscriptions = 0, cancel() ? (will restart when a new subscribe() is called)
});

// add an Engineering employee
await db.put({_id: 'jack', department: 'Engineering'});

// just newly-created people in engineering department
let subscription1 = await subscriptionMaster.subscribe('now');

subscription1.on('mutation', (mutation, doc, seq) => {
    if(mutation === 'UPSERT')
        console.log("New Engineering employee", doc._id);
    else if(mutation === 'DELETE')
        console.log("Engineering employee deleted", doc._id);	 
});

// all people in the engineering department
let subscription2 = await subscriptionMaster.subscribe(0);

let departmentUpToDate = false;
subscription2.on('find-complete', () => {
    departmentUpToDate = true;
    console.log("Check for existing engineers is done");
});

subscription2.on('mutation', (mutation, doc, seq) => {
    if(mutation === 'UPSERT') {
        if(!departmentUpToDate)
            console.log("Engineering employee found", doc._id);
        else
            console.log("New Engineering employee", doc._id); 
    }
    else if(mutation === 'DELETE')
        console.log("Engineering employee deleted", doc._id);	 
});

subscription2.on('error', (error) => {
	console.log("Error", error);
});

await db.put({_id: 'john', department: 'Finance'});

await db.put({_id: 'jill', department: 'Engineering'});