Do express partials have to be a separate file?

I'm trying to get my web server to pass changing values at 1 second intervals to the client.

The way I have it setup is the client inspects a variable which the server stores the values in. So far it's not working.

Are partials the way to go? If I use them then do I have to create a separate file?

For partials you have to use separate files, correct.

But in your case I would consider using pre-compiled Handlebars (or similar view engine) templates and load them only once for the entire app or for a specific route. This way you minimize IO and if they're pre-compiled, you get to render and serve them faster.