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0.0.3 • Public • Published


Immutable.js objects w/ Optimistic Updates for use in React/Flux or Vanilla javascript projects.

Getting Started

Install via git clone or npm:

npm install optimistic --save

Basic Usage

Create an Optimsitic object:

var Optimistic = require('optimistic');
var book = new Optimistic({ title: 'To Kill a Mockingbird', awards: 1 });
console.log(book.value); // { title: "To Kill a Mockingbird", awards: 1 }

Update the object synchronously using operations from Immutable JS:

book.update(function(book_map) {
  // Your update function receives an Immutable.fromJS() copy of the initial data
  // In this case, book_map is an instance of Immutable.Map
  return book_map.set('author', 'Harper Lee')
                 .set('awards', book_map.get('awards') + 1)
                 .set('followers', ['Kevin', 'Caleb']);
  // Note: these are immutable objects! If you aren't familiar, read the Immutable-JS docs!
console.log(book.value); // { title: "To Kill a Mockingbird", author: "Harper Lee", awards: 2, followers: ["Kevin", "Caleb"] }

Now push an async update:

var update_callbacks = book.pushUpdate(function(book_map) {
  // Add "Marcy", "Zach", and "Bill" to the middle
  book_map.get('followers').splice(1, 0, 'Marcy', 'Zach', 'Bill');
  return book_map;
// Look, the update is applied optimistically!
console.log(book.value); // { title: "To Kill a Mockingbird", ... followers: ["Kevin", "Marcy", "Zach", "Bill", "Caleb"] }
setTimeout(function fakeAPICall() {
  update_callbacks.failed(new Error("500: We don't like Marcy.")); // uh oh, there's an error from our 'server'.
  book.on('change', function(value, resolved_updates) {
    // Phew! Looks like the update is rolled back!
    console.log(value); // { title: "To Kill a Mockingbird", ... followers: ["Kevin", "Caleb"] }
    console.log(resolved_updates); // [ { succeeded: false, value: [Error: 500: We don't like Marcy.] } ]
}, 400);

A Few Notes:

Treat applying asynchronous updates as orderless. There should be never be any dependencies between async updates that are submitted concurrently.

If you need to push ordered updates, do it when you call the succeeded and failed callbacks that pushUpdate() returns or use pushUpdate()._promise.

Update resolution is asynchronous, so after executing a callback, the update will be permanently applied or rolled back on the next tick.

.on('change') fires after an update is resolved but only if it changes the value of the object.

Complex Updates

Optimistic is built so that you can do complex mutations as long as there are no dependencies between updates.

You can do everything from cascading filters on arrays or doing deep updates while preserving relative order upon rollbacks. It's OK if two operations are applied on the same fields, they just can't be dependent on order of execution.

[TBA example]

Usage with React/Flux

Optimistic was built so that optimistic UI updates with React and Flux would be really easy.

Optimistic objects are also event emitters, so use .on('change') to trigger change updates in your stores.

The change event takes 2 parameters: the current value of the Optimistic object the and a list of updates made during the last update resolution step.

Batching Update Resolutions

.pushUpdate(function() { ... }, true) -- passing in true as the second argument prevents updates from automatically resolving (applied permanently/rolled-back) after the callbacks execute.

If you have a large load of asynchronous events that you want to wait to return, you can gain a performance boost by preventing automatic resolution and then calling .resolveUpdates() to manually resolve all updates that have completed.


Open an issue or send a PR.


The MIT License

See LICENSE for details.

File an issue if you'd like an alternative license like the Apache 2.0


npm i optimistic

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