append-only-object

A way to append only objects (deltas) to objects

Why

I wanted to learn about javascript Proxies. As you can see, the tests are a bit funny as i started this side project after having my second children. And i didn't find similar libraries, so i made it public.

| Added some modifications to be aligned with Peer DID method specification.

Features

• The target object is not mutated
• The initial values can be set without id to be undeletables
• An id is added to all the objects appended if no id is included
• Can delete any object by his id
• Can append atomatically a timestamp setting opts.when to true
• Can't append deep equal object to an array,
• Can't append an object with an id already deleted

Installation

Available through the npm registry. It can be installed using the npm or yarn command line tools.

npm install append-only-object --save

Usage

import AppendOnlyObject from 'append-only-object'
 
const me = new AppendOnlyObject({ name: 'javi' })
 
me.append({ surname: [{ id: 'surname', value: 'Santos' }] })
me.append({ wife: 'Sam' })
me.append({ childrens: [{ value: 'Adam' }] })
const addSecondChildren = me.append({ childrens: [{ id: 'second', value: 'Matt' }] }, { patch: true, when: true, by: '1a75a182-9f48-4a18-bd1e-fea4b7f19e67' })
me.append({ errors: { id: 'error', value: 'An error' } })
me.delete('error')
 
me.name = 'noop'
delete me.name
me.wife = null
me.childrens[0].value = 'noop'
me.childrens.push({value: 'noop' })
 
console.log(me)
console.log(me.deleted)
console.log(addSecondChildren)

output:

{
  name: 'Javi',
  surname: [ { id: 'surname', value: 'Santos' } ],
  wife: 'Sam',
  childrens: [
    { value: 'Adam', id: 'uoNymdl6Q3W6vO-xL-Kwkw-2' },
    { value: 'Matt', id: 'second' }
  ]
}
Set { 'error' }
{
  change: { childrens: [ [Object] ] },
  by: '1a75a182-9f48-4a18-bd1e-fea4b7f19e67',
  when: '2020-06-25T12:40:52.430Z',
  patch: [ { op: 'add', path: '/childrens/1', value: [Object] } ]
}

See tests and example.js for more info.

API

new AppendOnlyObject(target, [options])

This class creates an append only object, where you can only append and "delete".

target is the initial object.

options to control the object returned by the append method, include:

{
  strict: true, // set to false if you want to be able to `modify` (without overwrite or delete) an object or array (ex. push to an array or add a prop to an existent object).
  unique: true, // set to false if you want to allow objects with the same id.
  encode: false, // to encode the `change` value. Other options json|base64url|base64|hex|binary
  by: false, // Can send an `string`, `object` or `array`.
  when: false, // add an (ISO 8601) `when` value.
  patch: false, // set to true if you want a (RFC6902) `patch` object tu be returned.
  previous: false, // set to true to receive the `previous` object before the append.
}

| All the options can be set globally in the creation of the object or with more priority (except strict and unique) in the append or delete methods.

append(delta, [options])

This method appends the delta to an already created AppendOnlyObject.

delete(id, [options])

The id can be a string or an array of strings.

Removes all matching object with this id. Adds the id to the AppendOnlyObject.deleted (the property is hidden, and is an iterable Set().

Tests

npm install
npm run test

License

MIT

Copyright (c) 2020 Javi Santos

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.