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# Abstract

persists JSON objects to a file . Keeps several files and loads older files if the latest is broken

## Contents

- [Meta](#Meta)
- [Class Persist](#Class-Persist)
  - [Parameters](#Persist-Parameters)
  - [Methods](#Persist-Methods)
    - [readData](#readData)
    - [saveObjectToFile](#saveObjectToFile)

## Meta

| | |
| --- | --- |
| **File** | persist.js |
| **Abstract** | persists JSON objects to a file . Keeps several files and loads older files if the latest is broken |
| **Author** | Volker Böhm |
| **Copyright** | Copyright ( c ) 2020 Volker Böhm |
| **License** | This software is licensed under the GNU LESSER GENERAL PUBLIC LICENSE Version 3 . It is furnished "as is" , without any support , and with no warranty , express or implied , as to its usefulness for any purpose . |

## Class Persist

`new Persist(configuration)`

Creates a new persistance support class

### Example

```javascript
const persist = new Persist( { keepFiles: 5 })
persist.saveObjectToFile('.', 'helloworld.json', { message: 'hello world' } )
const dataRead = persist.readData('.', 'helloworld.json')
// prints 'hello world'
console.log(dataRead.message)
```

### Persist Parameters

| Name | Type | Description |
| ---------- | ------------ | ----------------- |
| `configuration` | `Object` | configuration options | |

#### configuration properties

| Name | Type | Description |
| ---------- | ------------ | ----------------- |
| `keepFiles` | `number` | amount of file versions to keep ( including the recently written file ) | |

### Persist Methods

#### readData

`readData (directory, filenameBasis) => {Object}`

Reads data from a file

##### readData Parameters

| Name | Type | Description |
| ---------- | ------------ | ----------------- |
| `directory` | `string` | directory to delete file | |
| `filenameBasis` | `string` | basis filename of the file . The | |

##### readData returns

| Type | Description |
| ---- | ----------- |
| `Object` | the object read . |

#### saveObjectToFile

`async saveObjectToFile (directory, filenameBasis, objectToSave) => {undefined}`

Stringifies a JSON and writes it to a file . It will automatically add a timestamp to the provided "base" filename It does not throws errors , but logs write errors to the console

##### saveObjectToFile Parameters

| Name | Type | Description |
| ---------- | ------------ | ----------------- |
| `directory` | `string` | directory to delete file | |
| `filenameBasis` | `string` | basis filename of the file . The | |
| `objectToSave` | `Object` | object to save as JSON | |

##### saveObjectToFile returns

| Type | Description |
| ---- | ----------- |
| `undefined` |  |