retrieve timestamp from firebase database key

decode-firebase-database-key.js

// this is how firebase generates keys
// https://github.com/firebase/firebase-js-sdk/blob/master/packages/database/src/core/util/NextPushId.ts

const decodeFirebaseKey = key => {
  // chars firebase use for generating keys
  const CHARS = '-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz';

  let timestamp = 0
  
  // we only need to decode first 8 symbols
  for (let i = 0; i <= 7; i++) {
    const index = CHARS.indexOf(key[i])
    timestamp = timestamp * 64 + index
  }
  
  return timestamp
}