title: Create a unique ID for my child key in Firebase
body: <p>My users can create jobs. I want to add these jobs to my Firebase DB. I want the structure of the DB to look like this</p>
  
  <pre><code>- jobs
  --uid
  ---name
  ---descritpion
  ---...
  </code></pre>
  
  <p>For the "uid", I'd like a random and unique string. Is it possible to generate it automatically somehow instead of generating a random number by myself?</p>