How To Build Reactive Declarative Ui In Vanilla Javascript 2026
Modern UI frameworks offer abstraction layers that make user interfaces declarative and reactive. However, the web platform itself exposes primitives that can be composed to achieve similar patterns without introducing a dedicated UI library. This article demonstrates an experimental approach for creating a reactive, declarative UI flow using only vanilla JavaScript, Web APIs, and Proxy-based state tracking.
The purpose of the experiment is to examine how far native capabilities can be pushed without framework-level abstractions and to illustrate architectural benefits of declarative behavior in UI code: improved clarity, maintainability, and reduced coupling.
The experiment focuses on a practical business scenario:
Display a modal dialog that performs periodic polling of an API endpoint. The dialog should remain open until a specific condition is met, then resolve or reject accordingly.
The primary requirement is that consumer code defines what should happen, not how to wire it.
No framework is involved, yet responsibilities remain clearly segmented.
To keep high-level code focused on behavior, DOM creation is delegated to a lightweight utility:
This removes boilerplate from business logic and centralizes standard element configuration.
Next, the experiment introduces deep reactive state using the native Proxy object. This allows mutations at arbitrary depth to be observed without requiring explicit setters.
✔ enables deep mutation tracking ✔ does not require libraries ✔ keeps state as plain objects ✔ keeps consumer code minimal
Source: HackerNews
