is-fail/README.md

Tiny package implementing multiple strategies to verify if an HTTP request was failed

# is-fail [![Build Status](https://api.travis-ci.org/h2non/is-fail.svg?branch=master&style=flat)](https://travis-ci.org/h2non/is-fail) [![NPM](https://img.shields.io/npm/v/is-fail.svg)](https://www.npmjs.org/package/is-fail)

Tiny and dependency-free [node.js](http://nodejs.org)/[io.js](http://iojs.org) package implementing multiple strategies to verify if an HTTP request was failed, checking both error and HTTP response code.

Useful to combine as part of a retry/backoff logic. Also allows you to plug in additional strategies.

## Installation

```
npm install is-fail --save
```

## Usage

Simple usage as part of a retry mechanism
```js
const http = require('http')
const isFail = require('is-fail')()

function doRequest() {
  http.request('http://inconsistent-server', function (res) {
    if (isFail(null, res)) {
      return doRequest() // retry!
    }
    console.error('Response received')
  })
  .on('error', function (err) {
    if (isFail(err)) {
      return doRequest() // retry!
    }
    console.error('The request failed')
  })
}

doRequest()
```

Plug in additional strategies

```js
const http = require('http')
const isFail = require('is-fail')()

function notFoundStrategy(err, res) {
  return res.statusCode === 404
}

const checkFail = isFail([ notFoundStrategy ])

http.request('http://inconsistent-server', function (res) {
  if (checkFail(null, res)) {
    console.log('Failed request!')
  }
})
```

## API

#### isFail([ strategies ]) `=>` Function(err, res) `=>` Boolean

#### isFail.strategies `=` Array[ Strategy ]

#### isFail.check(strategies, err, res) `=>` Boolean

#### isFail.errors `=` Array[ ErrorStrategy ]

#### isFail.status `=` Array[ StatusStrategy ]

## License

MIT - Tomas Aparicio