object-observer

object-observer utility provides simple means to (deeply) observe specified object/array changes; implemented via native Proxy; changes delivered in a synchronous way

Usage no npm install needed!

<script type="module">
  import objectObserver from 'https://cdn.skypack.dev/object-observer';
</script>

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object-observer

object-observer provides a deep observation of a changes performed on an object/array graph.

Main aspects and features:

  • implemented via native Proxy (revokable)
  • observation is 'deep', yielding changes from a sub-graphs too
  • nested objects of the observable graph are observables too
  • changes delivered in a synchronous way by default, asynchronous delivery is optionally available as per Observable configuration; more details here
  • observed path may optionally be filtered as per observer configuration; more details here
  • original objects are cloned while turned into Observables
  • array specifics:
    • generic object-like mutations supported
    • intrinsic Array mutation methods supported: pop, push, shift, unshift, reverse, sort, fill, splice, copyWithin
    • massive mutations delivered in a single callback, usually having an array of an atomic changes
  • typed array specifics:
    • generic object-like mutations supported
    • intrinsic TypedArray mutation methods supported: reverse, sort, fill, set, copyWithin
    • massive mutations delivered in a single callback, usually having an array of an atomic changes
  • intrinsic mutation methods of Map, WeakMap, Set, WeakSet (set, delete) etc are not observed (see this issue for more details)
  • following host objects (and their extensions) are skipped from cloning / turning into observables: Date

Supported: CHROME71+ | FIREFOX65+ | EDGE79+ | SAFARI12.1 | NODE JS 12.0.0+

Performance report can be found here.

Changelog is here.

Preview

For a preview/playground you are welcome to:

  • CodePen - Observable.from() flavor
  • CodePen - new ObjectObserver() flavor

Install

Use regular npm install object-observer --save-prod to use the library from your local environment:

import { Observable } from 'node_modules/object-observer/dist/object-observer.min.js';

Alternatively, a CDN deployment available (AWS driven), so one can import it directly:

import { Observable } from 'https://libs.gullerya.com/object-observer/x.y.z/object-observer.min.js';

Note: replace the x.y.z with the desired version, one of the listed in the changelog.

CDN features:

  • security:
    • HTTPS only
    • intergrity checksums for SRI
  • performance
    • highly available (with many geo spread edges)
    • agressive caching setup

Full details about CDN usage and example are found here.

API

Library implements Observable API as it is defined here.

Additionally, from version 4.2.0 there is also 'DOM-like' API flavor - constructable ObjectObserver. This API is resonating with DOM's MutationObserver, ResizeObserver etc from the syntax perspective. Under the hood it uses the same Observable mechanics. Read docs about this API flavor here.

This is experimental API until specified otherwise.

Starting from 4.3.x object-observer is cross-instance operable. Observables created by different instances of the library will still be detected correctly as such and handled correctly by any of the instances.

Security

Security policy is described here. If/when any concern raised, please follow the process.

Examples

Objects
const
    order = { type: 'book', pid: 102, ammount: 5, remark: 'remove me' },
    observableOrder = Observable.from(order);

observableOrder.observe(changes => {
    changes.forEach(change => {
        console.log(change);
    });
});


observableOrder.ammount = 7;
//  { type: 'update', path: ['ammount'], value: 7, oldValue: 5, object: observableOrder }


observableOrder.address = {
    street: 'Str 75',
    apt: 29
};
//  { type: "insert", path: ['address'], value: { ... }, object: observableOrder }


observableOrder.address.apt = 30;
//  { type: "update", path: ['address','apt'], value: 30, oldValue: 29, object: observableOrder.address }


delete observableOrder.remark;
//  { type: "delete", path: ['remark'], oldValue: 'remove me', object: observableOrder }

Object.assign(observableOrder, { amount: 1, remark: 'less is more' }, { async: true });
//  - by default the changes below would be delivered in a separate callback
//  - due to async use, they are delivered as a batch in a single callback
//  { type: 'update', path: ['ammount'], value: 1, oldValue: 7, object: observableOrder }
//  { type: 'insert', path: ['remark'], value: 'less is more', object: observableOrder }
Arrays
let a = [ 1, 2, 3, 4, 5 ],
    observableA = Observable.from(a);

observableA.observe(changes => {
    changes.forEach(change => {
        console.log(change);
    });
});


//  observableA = [ 1, 2, 3, 4, 5 ]
observableA.pop();
//  { type: 'delete', path: [4], value: undefined, oldValue: 5, object: observableA }


//  now observableA = [ 1, 2, 3, 4 ]
//  following operation will cause a single callback to the observer with an array of 2 changes in it)
observableA.push('a', 'b');
//  { type: 'insert', path: [4], value: 'a', oldValue: undefined, object: observableA }
//  { type: 'insert', path: [5], value: 'b', oldValue: undefined, object: observableA }


//  now observableA = [1, 2, 3, 4, 'a', 'b']
observableA.shift();
//  { type: 'delete', path: [0] value: undefined, oldValue: 1, object: observableA }


//  now observableA = [ 2, 3, 4, 'a', 'b' ]
//  following operation will cause a single callback to the observer with an array of 2 changes in it)
observableA.unshift('x', 'y');
//  { type: 'insert', path: [0], value: 'x', oldValue: undefined, object: observableA }
//  { type: 'insert', path: [1], value: 'y', oldValue: undefined, object: observableA }


//  now observableA = [ 2, 3, 4, 'a', 'b' ]
observableA.reverse();
//  { type: 'reverse', path: [], object: observableA } (see below and exampe of this event for nested array)


//  now observableA = [ 'b', 'a', 4, 3, 2 ]
observableA.sort();
//  { type: 'shuffle', path: [], object: observableA } (see below and exampe of this event for nested array)


//  observableA = [ 2, 3, 4, 'a', 'b' ]
observableA.fill(0, 0, 1);
//  { type: 'update', path: [0], value: 0, oldValue: 2, object: observableA }


//  observableA = [ 0, 3, 4, 'a', 'b' ]
//  the following operation will cause a single callback to the observer with an array of 2 changes in it)
observableA.splice(0, 1, 'x', 'y');
//  { type: 'update', path: [0], value: 'x', oldValue: 0, object: observableA }
//  { type: 'insert', path: [1], value: 'y', oldValue: undefined, object: observableA }


let customer = { orders: [ ... ] },
    oCustomer = Observable.from(customer);

//  sorting the orders array, pay attention to the path in the event
oCustomer.orders.sort();
//  { type: 'shuffle', path: ['orders'], object: oCustomer.orders }


oCustomer.orders.reverse();
//  { type: 'reverse', path: ['orders'], object: oCustomer.orders }

Arrays notes: Some of array operations are effectively moving/reindexing the whole array (shift, unshift, splice, reverse, sort). In cases of massive changes touching presumably the whole array I took a pessimistic approach with a special non-detailed events: 'reverse' for reverse, 'shuffle' for sort. The rest of these methods I'm handling in an optimistic way delivering the changes that are directly related to the method invocation, while leaving out the implicit outcomes like reindexing of the rest of the Array.

Observation options

object-observer allows to filter the events delivered to each callback/listener by an optional configuration object passed to the observe API.

In the examples below assume that callback = changes => {...}.

let user = {
        firstName: 'Aya',
        lastName: 'Guller',
        address: {
            city: 'of mountaineers',
            street: 'of the top ridges',
            block: 123,
            extra: {
                data: {}
            }
        }
    },
    oUser = Observable.from(user);

//  path
//
//  going to observe ONLY the changes of 'firstName'
oUser.observe(callback, {path: 'firstName'});

//  going to observe ONLY the changes of 'address.city'
oUser.observe(callback, {path: 'address.city'});

//  pathsOf
//
//  going to observe the changes of 'address' own properties ('city', 'block') but not else
oUser.observe(callback, {pathsOf: 'address'});
//  here we'll be notified on changes of
//    address.city
//    address.extra

//  pathsFrom
//
//  going to observe the changes from 'address' and deeper
oUser.observe(callback, {pathsFrom: 'address'});
//  here we'll be notified on changes of
//    address
//    address.city
//    address.extra
//    address.extra.data