How Frontend Engineering Works Today
Explore how modern frontend engineering functions by understanding the client-side role, core parts like state and source of truth, and the fundamental fetch-state-render loop. Learn why determinism is crucial for predictable interfaces and how user actions integrate with server data to create dynamic user experiences.
The frontend is the part of an application that people actually see and use. It runs on the user's device, shows data, and responds to what the user does. Building one comes down to a small set of named parts and a loop that connects them. This lesson introduces both.
We'll cover the following:
What the frontend actually is
The vocabulary of the frontend layer
The loop: fetch, state, render
Why determinism is the property that matters
What the frontend actually is
The frontend is the layer of an application that runs on the user's device and handles everything the user sees and interacts with. It's often called the client, as opposed to the server, which runs elsewhere and holds the data.
That split is worth saying plainly, because it defines the boundary every later lesson works across. The frontend doesn't own the data. It asks for data, keeps a copy of it, and shows it. When the user does something, the frontend either updates its own copy or asks the server to make the change permanent.
This produces a constant back-and-forth. The client asks; the server answers. Nothing on screen got there without that exchange happening first.
Every piece of data a user sees began as one of ... ...