ngx-tansu

ngx-tansu is a lightweight, push-based state management library for Angular. It borrows the ideas and APIs originally designed and implemented by Svelte stores.

Main characteristics:

• small conceptual surface with expressive and very flexible API (functional and class-based);
• can be used to create "local" (module-level or component-level), collaborating stores;
• can handle both immutable and mutable data;
• results in compact code with the absolute minimum of boilerplate.

ngx-tansu is tightly integrated with the Angular ecosystem:

• works with the standard async pipe out of the box;
• stores can be registered in the DI container at any level (module or component injector).

Implementation wise, it is a tiny (500 LOC) library without any external dependencies.

Installation

You can add ngx-tansu to your project by installing the ngx-tansu package using your favorite package manager, ex.:

• yarn add ngx-tansu
• npm install ngx-tansu

Usage

Here is an example of a component using a ngx-tansu store:

import { Component } from "@angular/core";
import { Store, derived } from "ngx-tansu";

// A store is a class extending Store from ngx-tansu
class CounterStore extends Store<number> {
  constructor() {
    super(0); // initialize store's value (state)
  }

  // implement state manipulation logic as regular methods
  increment() {
    // create new state based on the current state
    this.update(value => value + 1);
  }

  reset() {
    // replace the entire state with a new value
    this.set(0);
  }
}

@Component({
  selector: "my-app",
  template: `
    <button (click)="counter$.increment()">+</button> <br />

    <!-- store values can be displayed in a template with the standard async pipe -->
    Counter: {{ counter$ | async }} <br />
    Double counter: {{ doubleCounter$ | async }} <br />
  `
})
export class AppComponent {
  //  A store can be instantiated directly or registered in the DI container
  counter$ = new CounterStore();

  // One can easily created derived (computed) values by specifying dependant stores and a transformation function
  doubleCounter$ = derived(this.counter$, value => 2 * value);
}

While being fairly minimal, this example demonstrates most of the ngx-tansu APIs.

Check the documentation for the complete API and more usage examples.

Contributing to the project

Please check the DEVELOPER.md for documentation on building and testing the project on your local development machine.

Credits and the prior art

• Svelte gets all the credit for the initial idea and the API design.
• NgRx component stores solve a similar problem with a different approach.