# @syncthetic/emitter

> To get started, install the package `npm i @syncthetic/emitter`

Latest version **0.0.2** (published 2018-11-15) · 0 weekly downloads

## Install

```sh
npm install @syncthetic/emitter
pnpm add @syncthetic/emitter
yarn add @syncthetic/emitter
bun add @syncthetic/emitter
```

## Health

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

Positive: has types; esm support; no vulnerabilities.

Warnings: low downloads; pre 1.0.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 0.0.2 |
| Published | 2018-11-15 |
| First published | 2018-11-15 |
| Weekly downloads | 0 |
| TypeScript types | bundled |
| Module format | ESM + CommonJS |
| Dependencies | 1 |
| Unpacked size | 61.2 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| Maintainers | besstech |

## Links

- npm: https://www.npmjs.com/package/@syncthetic/emitter
- npm.io page: https://npm.io/package/@syncthetic/emitter

## Dependencies (1)

- [tslib](https://npm.io/package/tslib.md) ^1.9.0

## Recent versions

- 0.0.2 (latest) — 2018-11-15
- 0.0.1 — 2018-11-15

## README

### @syncthetic/emitter
#### An angular library to watch for event changes. Fire events when a defined event returns `true`

To get started, install the package
`npm i @syncthetic/emitter`

importing the emitter service
`import { EmitService } from '@syncthetic/emitter'`

constructor config, of course...
`constructor ( private emitter: EmitService, ... ) {}`

Triggers and their options are configured in the following `interface` format

```
interface Trigger {
  check: Function,
  callback: Function
  options?: TriggerOptions
}
```
```
interface TriggerOptions {
  originalValue?: any,
  newValue?: any,
  dataSet?: any
}
```
To set up our event emitter, a few things need to be established.

You need a `compare function`, which will be run by the `EmitService` defined as the `Trigger.check` value. The function should return a `boolean` based value. When this function return `true`, the `Trigger.callback` function will be called. If `Trigger.options` exist and are defined, it will be passed into the `check` and `callback` functions.

### Let's see some code...

In this exmaple, I have designed a small snippet, which runs on an `array` of numbers to detect if a change occured at a specific index.

```
numbers_differ ( options ) {
  console.log('would compare', options.originalValue, ' with ', options.dataSet.data[1])
  options.newValue = options.dataSet.data[1]
  return options.originalValue !== options.dataSet.data[1]
}

show_number_differs ( options ) {
  alert( options.originalValue + ' does not equal ' + options.newValue )
}
  
this.emit.add_trigger({
    check: this.numbers_differ,
    callback: this.show_number_differs,
    options: { originalValue: this.data.data[1], dataSet: this.data }
})
// starts the EmitterService to check for triggers
this.emit.trigger_loop()
```
Here's what we did
1. We initialized a trigger to watch the the `array` (`this.data.data[1]`) value at index 1
2. We pass in the `options`, to our `check` function so we can see the `originalValue` and `dataSet` (the `array` to monitor), and to be able to set the `newValue` from the `callback` function.

Here is the `data.service.ts` file generating our `data.data` list.

```
export class DataService {

  data: Number[] = []
  constructor() { 
    this.start_randomizing()
    this.show_data()
  }

  generate_data () {
    console.log('generating data')
    const new_data = []
    for (let i = 1; i < 10; i++) {
      const n = Math.floor(Math.random()*(999-100+1)+100)
      new_data.push(n)
    }
    this.data = new_data
  }
  
  start_randomizing () {
    setInterval(this.generate_data.bind(this), 3000)
  }
}
```

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