title: MongoDB empty string value vs null value
body: <p>In MongoDB production, if a value of a key is empty or not provided (optional), should I use empty string value or should I use null for value.</p>
  
  <p>1) Is there any pros vs cons between using empty string vs null?</p>
  
  <p>2) Is there any pros vs cons if I set value to undefined to remove properties from your existing doc vs letting properties value to either empty string or null?</p>
  
  <p>Thanks</p>