How to check if js code is running on node server or on the client

Question

How to check if js code is running on node server or on the client

I want to determine whether my js code is running on the node server or on the client, and store it into a variable isServer = true 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?

Thanks for help!

javascript
node.js

Answer 1

You could use this:

function is_server() {
   return ! (typeof window != 'undefined' && window.document);
}

As the global window.document object is only present in the browser context.