TypeScript FSA [![npm version][npm-image]][npm-url] [![Build Status][travis-image]][travis-url]

Action Creator library for TypeScript. Its goal is to provide type-safe experience with Flux actions with minimum boilerplate.
Created actions are FSA-compliant:

``ts
interface Action {
type: string;
payload: Payload;
error?: boolean;
meta?: Object;
}
`

Installation

`
npm install --save typescript-fsa
`

Usage

$3

`ts
import actionCreatorFactory from 'typescript-fsa';

const actionCreator = actionCreatorFactory();

// Specify payload shape as generic type argument.
const somethingHappened = actionCreator<{foo: string}>('SOMETHING_HAPPENED');

// Get action creator type.
console.log(somethingHappened.type); // SOMETHING_HAPPENED

// Create action.
const action = somethingHappened({foo: 'bar'});
console.log(action); // {type: 'SOMETHING_HAPPENED', payload: {foo: 'bar'}}
`

$3

Async Action Creators are objects with properties started, done and
failed whose values are action creators. There is a number of Companion Packages that help with binding Async Action Creators to async processes.

`ts
import actionCreatorFactory from 'typescript-fsa';

const actionCreator = actionCreatorFactory();

// specify parameters and result shapes as generic type arguments
const doSomething =
actionCreator.async<{foo: string}, // parameter type
{bar: number}, // success type
{code: number} // error type
>('DO_SOMETHING');

console.log(doSomething.started({foo: 'lol'}));
// {type: 'DO_SOMETHING_STARTED', payload: {foo: 'lol'}}

console.log(doSomething.done({
params: {foo: 'lol'},
result: {bar: 42},
}));
// {type: 'DO_SOMETHING_DONE', payload: {
// params: {foo: 'lol'},
// result: {bar: 42},
// }}

console.log(doSomething.failed({
params: {foo: 'lol'},
error: {code: 42},
}));
// {type: 'DO_SOMETHING_FAILED', payload: {
// params: {foo: 'lol'},
// error: {code: 42},
// }, error: true}
`

$3

You can specify a prefix that will be prepended to all action types. This is
useful to namespace library actions as well as for large projects where it's
convenient to keep actions near the component that dispatches them.

`ts
// MyComponent.actions.ts
import actionCreatorFactory from 'typescript-fsa';

const actionCreator = actionCreatorFactory('MyComponent');

const somethingHappened = actionCreator<{foo: string}>('SOMETHING_HAPPENED');

const action = somethingHappened({foo: 'bar'});
console.log(action);
// {type: 'MyComponent/SOMETHING_HAPPENED', payload: {foo: 'bar'}}
`

$3

`ts
// actions.ts
import actionCreatorFactory from 'typescript-fsa';

const actionCreator = actionCreatorFactory();

export const somethingHappened =
actionCreator<{foo: string}>('SOMETHING_HAPPENED');
export const somethingAsync =
actionCreator.async<{foo: string},
{bar: string}
>('SOMETHING_ASYNC');


// reducer.ts
import {Action} from 'redux';
import {isType} from 'typescript-fsa';
import {somethingHappened, somethingAsync} from './actions';

type State = {bar: string};

export const reducer = (state: State, action: Action): State => {
if (isType(action, somethingHappened)) {
// action.payload is inferred as {foo: string};

action.payload.bar; // error

return {bar: action.payload.foo};
}

if (isType(action, somethingAsync.started)) {
return {bar: action.payload.foo};
}

if (isType(action, somethingAsync.done)) {
return {bar: action.payload.result.bar};
}

return state;
};
`

#### redux-observable

`ts
// epic.ts
import {Action} from 'redux';
import {Observable} from 'rxjs';
import {somethingAsync} from './actions';

export const epic = (actions$: Observable) =>
actions$.filter(somethingAsync.started.match)
.delay(2000)
.map(action => {
// action.payload is inferred as {foo: string};

action.payload.bar; // error

return somethingAsync.done({
params: action.payload,
result: {
bar: 'bar',
},
});
});
`

Companion Packages

* typescript-fsa-redux-saga
* typescript-fsa-redux-observable
* typescript-fsa-redux-thunk
* typescript-fsa-reducers

Resources

* Type-safe Flux Standard Actions (FSA) in React Using TypeScript FSA
* Type-safe Asynchronous Actions (Redux Thunk) Using TypeScript FSA

API

$3

Creates Action Creator factory with optional prefix for action types.

* prefix?: string: Prefix to be prepended to action types as /.
* defaultIsError?: Predicate: Function that detects whether action is error
given the payload. Default is payload => payload instanceof Error.

$3

Creates Action Creator that produces actions with given type and payload of type Payload.

* type: string: Type of created actions.
* commonMeta?: object: Metadata added to created actions.
* isError?: boolean: Defines whether created actions are error actions.

$3

Creates three Action Creators:
* started: ActionCreator
* done: ActionCreator<{params: Params, result: Result}>
* failed: ActionCreator<{params: Params, error: Error}>

Useful to wrap asynchronous processes.

* type: string: Prefix for types of created actions, which will have types ${type}_STARTED, ${type}_DONE and ${type}_FAILED.
* commonMeta?: object: Metadata added to created actions.

$3

Creates action with given payload and metadata.

* payload: Payload: Action payload.
* meta?: object: Action metadata. Merged with commonMeta of Action Creator.

$3

Returns true if action has the same type as action creator. Defines
Type Guard
that lets TypeScript know payload type inside blocks where isType returned
true:

`ts
const somethingHappened = actionCreator<{foo: string}>('SOMETHING_HAPPENED');

if (isType(action, somethingHappened)) {
// action.payload has type {foo: string}
}
`

$3

Identical to isType except it is exposed as a bound method of an action
creator. Since it is bound and takes a single argument it is ideal for passing
to a filtering function like Array.prototype.filter or
RxJS's Observable.prototype.filter.

`ts
const somethingHappened = actionCreator<{foo: string}>('SOMETHING_HAPPENED');
const somethingElseHappened =
actionCreator<{bar: number}>('SOMETHING_ELSE_HAPPENED');

if (somethingHappened.match(action)) {
// action.payload has type {foo: string}
}

const actionArray = [
somethingHappened({foo: 'foo'}),
somethingElseHappened({bar: 5}),
];

// somethingHappenedArray has inferred type Action<{foo: string}>[]
const somethingHappenedArray = actionArray.filter(somethingHappened.match);
`

For more on using Array.prototype.filter` as a type guard, see
this github issue.

[npm-image]: https://badge.fury.io/js/typescript-fsa.svg
[npm-url]: https://badge.fury.io/js/typescript-fsa
[travis-image]: https://travis-ci.org/aikoven/typescript-fsa.svg?branch=master
[travis-url]: https://travis-ci.org/aikoven/typescript-fsa