We used to, the idea being we could reproduce validation in JavaScript and Python. It kind of worked but it wasn't that clean. Ended up switching the server to

We used to, the idea being we could reproduce validation in JavaScript and Python. It kind of worked but it wasn't that clean. Ended up switching the server to Marshmallow schemas and just having more custom logic on the client side. It's a classic DRY ... this is where "duplicate" code was better for more control and less shoehorning.