var-persist/README.md

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  ### Persist

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  Typescript Library to Sync Variables with LocalStorage

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## Table of Contents
- [Persist](#top)
	- [About](#about)
      - [Examples](#examples) 
      - [Built With](#built-with)
	- [Setup](#setup)
      - [Production](#production)
      - [Development](#development)
    - [Documentation](#documentation)
      - [Classes](#classes)
      - [Decorators](#decorators)
      - [Types](#types)
	- [License](#license)

## About

Persist is an updated version of [webstorage-decorators](https://git.zakscode.com/ztimson/webstorage-decorators), a library which saves variables to local or session storage.

This library aims to improve upon the original's limitations by using the new [Proxy Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy). Improvements include:
 - Supports both objects & decorators
 - Proxy object ensures all changes are tracked including impure functions
 - [Proto]types and functions can be preserved by passing the `type` option

JavaScript's decorators are currently undergoing changes to the API overseen by [TC39](https://tc39.es) and currently have no support for property decorators. [Experimental decorators](https://www.typescriptlang.org/tsconfig#experimentalDecorators) must be enabled to work properly.

### Examples

Using objects:
```ts
import {Persist} from 'ztimson/persist';

// Proxy Object (Always access/modify using `.value`):
let theme = new Persist<string>('theme', {default: 'os'});

console.log(theme.value) // Output: os
theme.value = 'light'; // Changes will be synced to localStorage['theme'];
```

Using decorators:
```ts
import {persist} from 'ztimson/persist';

// Using decorators
class Theme {
	@persist({key: 'theme', default: 'os'}) current!: string;
}
const theme = new Theme();

console.log(theme.current); // Output: light
theme.current = 'dark'; // You can ommit `.value` when using the decorator
```

Advanced uses:

```ts
import {Persist} from 'ztimson/persist';

// Options are the same for both the persist decorator and object:
let example = new Persist<string[]>('example', {
	storage: SessionStorage, // Use a different storage solution
	default: [], // Default value if stored value === undefined
	type: Array // Ensures [proto]type & methods are restored
});

// Callback when changes are made
example.watch(value => console.log(`Length - ${value.length}`));
example.value = [1, 2, 3];
// Output: Length - 3
example.value.pop(); // Impure changes are saved
// Output: Length - 2

```

### Built With
[![TypeScript](https://img.shields.io/badge/TypeScript-3178C6?style=for-the-badge&logo=typescript&logoColor=white)](https://typescriptlang.org/)

## Setup

<details>
<summary>
  <h3 id="production" style="display: inline">
    Production
  </h3>
</summary>

#### Prerequisites
- [Node.js](https://nodejs.org/en/download)

#### Instructions
1. Install persist: `npm i ztimson/persist`
2. Enable decorators inside `tsconfig.json`:
```json
{
	"compilerOptions": {
		"experimentalDecorators": true,
		...
	},
	...
}
```
3. Import & use, see [examples above](#examples)

</details>

<details>
<summary>
  <h3 id="development" style="display: inline">
    Development
  </h3>
</summary>

#### Prerequisites
- [Node.js](https://nodejs.org/en/download)

#### Instructions
1. Install the dependencies: `npm i`
2. Build library & docs: `npm build`
3. Run unit tests: `npm test`

</details>

## Documentation

<details>
<summary>
  <h3 id="classes" style="display: inline">
    Classes
  </h3>
</summary>

Create a proxy object which wraps your data so any changes can be intercepted & synced with storage.

Your data is stored under the `value` property and should always be accessed/modified through it.

#### Example

```ts
import {Persist} from 'ztimson/persist'

const theme = new Persist('theme.current', {default: 'os'});

console.log(theme.value); // Output: os
theme.value = 'light'; // Make sure you always use .value to access/modify data

location.reload(); // Simulate refresh
console.log(theme.value); // Output: light
```

#### Constructor

`Persist<T>(key: string, options?: PersistOptions)`

| Argument  | Type                                             | Description                                                 |
|-----------|--------------------------------------------------|-------------------------------------------------------------|
| `key`     | `string`                                         | Primary key value will be stored under                      |
| `options` | [`PersistOptions<T>`](../Home.md#persistoptions) | Configure using [PersistOptions](../Home.md#persistoptions) |


#### Properties

| Name      | Type                                             | Description                                                 |
|-----------|--------------------------------------------------|-------------------------------------------------------------|
| `key`     | `string`                                         | Primary key value will be stored under                      |
| `options` | [`PersistOptions<T>`](../Home.md#persistoptions) | Configure using [PersistOptions](../Home.md#persistoptions) |
| `value`   | `T`                                              | Current value                                               |

#### Methods

##### clear

Delete value from storage

`clear(): void`

##### load

Load value from storage

`load(): void`

##### save

Save current value to storage

`save(): void`

##### watch

Register callback to listen for changes

`watch(fn: (value: T) => void): void`

#### Parameters

| Name | Type |
| :------ | :------ |
| `fn` | (`value`: `T`) => `any` |

##### toString

Return value as JSON string

`toString(): string`

###### Returns

`string` - Stringified JSON object

##### valueOf

Return current value

`valueOf(): T`

###### Returns

`T` - Current value

</details>

<details>
<summary>
  <h3 id="decorators" style="display: inline">
    Decorators
  </h3>
</summary>

`persist(options?: {key?: string} & PersistOptions<T>)`

</details>

<details>
<summary>
  <h3 id="types" style="display: inline">
    Types
  </h3>
</summary>

`PersistOptions<T>`

Configurable options to change persistence behavior

| Property   | Type      | Description                                                                            |
|------------|-----------|----------------------------------------------------------------------------------------|
| `default?` | `T`       | Default/Initial value if undefined                                                     |
| `storage?` | `Storage` | Storage implementation, defaults to LocalStorage. Can also be used with SessionStorage |
| `type?`    | `any`     | Force value to have \[proto\]type                                                      |

</details>

## License

Copyright © 2023 Zakary Timson | Available under MIT Licensing

See the [license](./LICENSE) for more information.