title: How to check if js code is running on node server or on the client
body: <p>I want to determine whether my js code is running on the node server or on the client, and store it into a variable <code>isServer = true</code> if it is running on the server. How can I do that? Is there a way to simply check for the existence of a property that is only available on the server and, if this is possible, which is the best option?</p>
  
  <p>Thanks for help!</p>