# @xtream/yaem

> Pure javascript porting of @ngrx/entity to use also with React

Latest version **1.1.0** (published 2019-10-02) · 0 weekly downloads

## Install

```sh
npm install @xtream/yaem
pnpm add @xtream/yaem
yarn add @xtream/yaem
bun add @xtream/yaem
```

## Health

**Score 25/100 (F)** — status: abandoned.

Positive: has types; esm support; no vulnerabilities.

Warnings: low downloads.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 1.1.0 |
| Published | 2019-10-02 |
| First published | 2019-07-05 |
| Weekly downloads | 0 |
| TypeScript types | bundled |
| Module format | ESM + CommonJS |
| Dependencies | 0 |
| Unpacked size | 266.5 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 7 |
| Author | Luca Micieli |
| Maintainers | xtream |
| Keywords | entities, redux, ngrx, reselect, memoization |

## Links

- npm: https://www.npmjs.com/package/@xtream/yaem
- Repository: https://github.com/xtreamsrl/yaem
- Homepage: https://github.com/xtreamsrl/yaem#readme
- Issues: https://github.com/xtreamsrl/yaem/issues
- npm.io page: https://npm.io/package/@xtream/yaem

## Recent versions

- 1.1.0 (latest) — 2019-10-02
- 1.0.1 — 2019-09-23
- 1.0.0 — 2019-09-23
- 0.0.2 — 2019-07-06
- 0.0.1 — 2019-07-05

## README

# yaem

yaem (Yet Another Entity Manager) is a pure  @ngrx/entity porting that removes the Angular and @ngrx/store dependency
so that it can be used also in React project.

The two most important feature are Memoized selectors and an entity adapter a simple utils that allows to manage entity 
in store preserving immutability.

## Memoized selector (as reselect)

Memoized selectors allows to improve React performance, reducing application rerendering. If the input state is not changed
the memoized selector just returns the precomputed value without recalculate it, preserving object reference and thus 
allowing memoized components and Pure component to not rerender.

### Feature selector

The feature selector must me the root selector of each one. It selects the part of the state under the key specificied in 
the string as first argument. If for example the state has a root key named `user`:
 
```typescript jsx
import {createFeatureSelector} from '@xtream/yeam';
import {UserState} from '../reducers';

const selectUserState = createFeatureSelector<UserState>('user');

```

### Simple selector

The createSelector api compose selector together memoizing each step and returning a function.

```typescript jsx
import {createFeatureSelector, createSelector} from '@xtream/yeam';
import {UserState} from '../reducers';

const selectUserState = createFeatureSelector<UserState>('user');

const selectName = createSelector(
  selectUserState,
  state => state.name
);

const selectSurname = createSelector(
    selectUserState,
    state => state.surname
);

const selectCompleteName = createSelector(
    selectName,
    selectSurname,
    (name, surname) => `${name} ${surname}`
);

```

## Entity adapter

The entity adampter is an utility to easely manage entity in state keeping immutability. The exposed methos are

| Method | Usage| 
|--------|-----------|
| removeAll | Clear all the entity in state|
| addOne | Add one entity|
| addMany | Add more entity
| addAll | Overwrite all the entity with the provided ones|
| updateOne | Update an entity (do nothing if not exist)|
| updateMany| Update all the provided entity (do nothing if not exist)|
| upsertOne | Update if exits or add if not exists |
| upsertMany | Update the ones that exists ad add the others|
| removeOne | Remove entity |
| removeMany | Remove all the provided entity |
| map | Transform all the entity using the provided function|


All these methods require the state as a parameter. Each entity is assumed to have an id property but you can provide
a selectId function to use a custom id using constructor.

For performance reason the entity state is organized like this:
```typescript jsx

{
  ids: any[],
  entities : {
    [id:any]: Entity
  }
}
```
Single update, add, or retrieve are realy fast thanks to the entities map object while ids array is used to 
keey track of all the present entity (or to keep them in a specific order).

To let the application access the state the entity adapter exposes 4 selectors:

| Selector | Usage| 
|--------|-----------|
| selectIds| Get the list of all ids|
| selectEntities| Get the dictionary of all the entity|
| selectAll| Get the complete list of entities|
| selectTotal| Get the number o entity in the state|

### Complete example

```typescript jsx
import {createEntityAdapter, EntityState} from '@xtream/yaem';
import {User} from '../models';
import * as usersActions from '../actions'

interface UsersState extends EntityState<User> {
  selectedUserId: string | null;
}

const adapter = createEntityAdapter<User>({
  selectId: user => user.username,
  sortComparer: (userA, userB) => userA.subscriptionDate.localeCompare(userB.subscriptionDate)
});

const defaultState = adapter.getInitialState({selectedUserId: null});

export default function reducer(state: UsersState = defaultState, action: usersActions.UsersActionTypes): UsersState {

  switch (action.type) {
    case usersActions.ADD_USER_SUCCESS:
      return adapter.addOne(action.user, state);
    case usersActions.DELETE_USER_SUCCESS:
      return adapter.removeOne(action.username, state);
    case usersActions.UPDATE_USER_SUCCESS:
      return adapter.upsertOne(action.user, state);
    default:
      return state;
  }
}

const {    
  selectIds,
  selectEntities,
  selectAll,
  selectTotal
} = adapter.getSelectors();

export {
  selectIds,
  selectEntities,
  selectAll,
  selectTotal
};





```

---
_Source: https://npm.io/package/@xtream/yaem · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._