is-error-code 
Check if an HTTP status code is an error code
Install
$ npm install --save is-error-code
Usage
var isErrorCode = require('is-error-code')
isErrorCode(200)
//=> false
isErrorCode(400)
//=> true
API
isErrorCode(code) -> boolean
code
Required
Type: number
An HTTP status code.
License
MIT Ben Drucker