firebase-validate-key 
Validate that a string is a valid Firebase key
Install
$ npm install --savefirebase-validate-key
Usage
var validate = require('firebase-validate-key')
validate('foo') // => true
validate('#foo') // => false
API
validate(key) -> boolean
key
Required
Type: string
False if the key is empty or is ., $, #, [, ], or /. Otherwise true.