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https://github.com/gxsshallot/specials

A tool to manage general or special handle.
https://github.com/gxsshallot/specials

generals handling specials

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A tool to manage general or special handle.

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# specials

[![npm version](https://img.shields.io/npm/v/specials.svg?style=flat)](https://www.npmjs.com/package/specials)
[![Build Status](https://travis-ci.org/gaoxiaosong/specials.svg?branch=master)](https://travis-ci.org/gaoxiaosong/specials)

A tool to manage general or special handle.

## Install

Install by Yarn:

```shell
yarn add specials
```

Install by NPM:

```shell
npm install --save specials
```

## Usage

Import the module in file:

```javascript
import * as Specials from 'specials';
```

### Storage

We use a root object to store all information. In each node, we can store a default handle and an array of special handles.

* `Specials.DEFAULT_HANDLE`: Key for default handle.
* `Specials.SPECIAL_PART`: Key for part of special handle.

Here is an example of a root object:

```
{
[DEFAULT_HANDLE]: function f0 {.....},
display: {
text: {
[DEFAULT_HANDLE]: function f1 {.....},
phone: {
[DEFAULT_HANDLE]: function f4 {.....},
},
},
[SPECIAL_PART]: [
{
[kSpecial]: state => state === 'user',
[kHandle]: function f2 {...},
[kId]: 1,
[kPriority]: 0,
},
{
[kSpecial]: state => state === 'org',
[kHandle]: function f3 {...},
[kId]: 2,
[kPriority]: 1,
}
],
},
edit: {
...
},
}
```

Each special part consists of four keys:

* `Specials.kId`: Identifier of handle. Used for unregister the handle.
* `Specials.kSpecial`: Special judging function. Returns a boolean.
* `Specials.kHandle`: Handle function when special function is valid.
* `Specials.kPriority`: Prority of handle when multi items are valid. Larger one will be used first. You can use `Specials.PRIORITY`.

### API

* `register: (obj, path, special, handle, priority) => number | void`: Register a default or special handle with priority. Return `handleId` if `special` is not `null`.
* `unregister: (obj, path, handleId) => boolean`: Unregister a default or special handle. Return true when succeed.
* `get: (obj, path, state, params) => any`: Get handle with a `state`. Then uses handle function with `params` or just returns the handle object.

### Example

First, initialize a root object:

```javascript
const rootNode = {};
```

Register different handle:

```javascript
Specials.register(rootNode, [], undefined, y => y);
Specials.register(rootNode, 'display', undefined, y => y + 1);
Specials.register(rootNode, ['display', 'text'], undefined, y => y + 2);
Specials.register(rootNode, 'display', x => x === 1, y => y - 1); // return: 1
Specials.register(rootNode, ['display', 'text'], x => x === 2, 'P1'); // return: 1
Specials.register(rootNode, ['display', 'text'], x => x === 2, 'P2', Specials.PRIORITY.HIGH); // return: 2
```

The root object will be:

```
{
[DEFAULT_HANDLE]: y => y,
display: {
[DEFAULT_HANDLE]: y => y + 1,
text: {
[DEFAULT_HANDLE]: y => y + 2,
[SPECIAL_PART]: [
{
[kSpecial]: x => x === 2,
[kHandle]: 'P1',
[kId]: 1,
[kPriority]: 0,
},
{
[kSpecial]: x => x === 2,
[kHandle]: 'P2',
[kId]: 2,
[kPriority]: 255,
},
],
},
[SPECIAL_PART]: [
{
[kSpecial]: x => x === 1,
[kHandle]: y = y - 1,
[kId]: 1,
[kPriority]: 0,
},
],
},
}
```

Then use `get` to get handle:

```javascript
Specials.get(rootNode, [], undefined, undefined); // function: y => y
Specials.get(rootNode, [], undefined, 100); // y=>y result: 100
Specials.get(rootNode, ['display'], undefined, 100); // y=>y+1 result: 101
Specials.get(rootNode, ['parse'], undefined, 100); // y=>y result: 100
Specials.get(rootNode, ['display'], 1, 100); // y=>y-1 result: 99
Specials.get(rootNode, ['display'], 2, 100); // y=>y+1 result: 101
Specials.get(rootNode, ['display', 'text'], 1, 100); // y=y-1 result: 99
Specials.get(rootNode, ['display', 'text'], 2, 100); // 'P2' result: 'P2'
```

Finally we can unregister default or special handle:

```javascript
Specials.unregister(rootNode, []);
Specials.unregister(rootNode, 'display');
Specials.unregister(rootNode, ['display', 'text']);
Specials.unregister(rootNode, 'display', 1); // return: true
Specials.unregister(rootNode, ['display', 'text'], 1); // return: true
Specials.unregister(rootNode, ['display', 'text'], 2); // return: true
Specials.unregister(rootNode, ['display', 'text'], 3); // return: false
```