title: How to safely allow the use of $ sign within mongoDB
body: <p>We have a project which uses a nodeJS and MongoDB backend.</p>
  <p>This project ideally needs to allow users to input $ signs into the comments which they can make.</p>
  <p>However I am concerned that this could result in query injection.</p>
  <p>Is there a safe way to allow the use of $ signs?</p>