node-status-codes 
Node.js
http.STATUS_CODES
ponyfill
Ponyfill: A polyfill that doesn't overwrite the native method
The built-in list of HTTP status codes differ between Node.js versions, so this is a good way to make sure it's consistent. Will be kept up to date with latest Node.js.
Install
$ npm install --save node-status-codes
Usage
var nodeStatusCodes = require('node-status-codes');
console.log(nodeStatusCodes[200]);
//=> 'OK'
console.log(nodeStatusCodes[500]);
//=> 'Internal Server Error'
License
MIT © Sindre Sorhus