EPromise

A simple promise extension with tuple state and centralized error handling supports in size less than 3kb.

Introduction

Primary scopes
- Tuple supports
  
  resolve / reject with multiple values, passing directly to thenable callbacks, for example
```
EPromise((resolve, reject) => succeed ? resolve(result, meta) : reject(errors))
        .onERR(processWithErrors)
        .then(processWithResultAndMeta)
```
- Centralized error handling
  
  We already have UnhandledRejection and NodeJS equivalent, read this for more information
  
  Any of these system-wide solutions seems not suitable for apps in most scenarios, this extension can take care of this simpler and lightweight
  
  Promise rejection will all be handled by default uncaught (registered in the prototype), without any global pollution
Other extensions

Such as onRTN / onERR / fin, and more extensions can be added easily, see the documentation.

Compatibility

IE6+ (polyfills required for ES7- browsers)
NodeJS

Limitation

async await interoperation

only the first of the tuple could be seen by await

console.log(await EPromise.resolve(1, 2)); // output 1

try {
    await EPromise.reject(1, 2);
} catch (e) {
    console.log(e); // output 1      
}

await for rejected promise doesn't trigger registered default uncaught handler, but system-wide UnhandledRejection would

// expected behaviour: handled by default uncaught, such as output `Uncaught (in promise): 1` in error console   
EPromise.reject(1);

// default uncaught not called, an exception is thrown here instead 
await EPromise.reject(1);
                                                           
// workaround: add `onERR` at last, default uncaught would be called, but promise state changes to resolved 
const result = await EPromise.reject(1).onERR(null); // result is `null`, no exception thrown, you have to check null

Install

npm install e-promises

Usage

Bundler (webpack etc)

esm (recommended)
```
import EPromise from 'e-promises'
```
CommonJS
```
const EPromise = require('e-promises')
```

NodeJS

CommonJS (recommended)
```
const EPromise = require('e-promises')
```
ESM

Now Nodejs does not support ESM module import directly, if you are willing to import the ESM version, you have to specify the full file name with extension
```
import EPromise from 'e-promises/lib/promise.mjs'
```

Web browser with no bundler

The ancient browser (with polyfills)

<!-- src="path/to/EPromise.all.min.js" -->
<script src="dist/EPromise.all.min.js"></script>
<!--suppress JSUnresolvedVariable -->
<script>
EPromise.resolve(); // ...
</script>

see this example

if polyfills are not required (etc. injected in another way), the smallest version dist/EPromise.min.js should be used.

Modern browser with esm supports

<!--suppress ES6UnusedImports, JSUnresolvedVariable -->
<script type="module">
// from 'path/to/promise.mjs'
import EPromise from './lib/promise.mjs';

EPromise.resolve(); // ...
</script>