Can you modify app.locals variables on the client side in a node app?

I’m using express-handlebars and I want to set some app.locals variables to being false. In my views I want to be able to change them to true depending on certain form selections so that some extra form elements wrapped in {{#if }} blocks will be rendered.

Is it possible to modify app.locals on the client side? Or should I just stick to some client side JS to hide the forms instead?