Lit and Tooling

Vanilla Custom Elements are powerful but verbose — updating the DOM on every state change requires manual work. Lit is a ~5 KB library that adds three things: reactive properties (declare once, re-render automatically), declarative lit-html templates (efficient DOM diffing), and scoped styles (Shadow DOM CSS with zero leakage).

How Lit updates the DOM

When a reactive property changes, Lit does not immediately re-render. Instead it schedules a microtask update, checks whether an update is needed, runs your render() method, diffs the result with the previous render, and then calls the updated() hook if you defined one.

flowchart LR
  PropChange["Property
changes"] --> Schedule["Schedule
microtask
update"]
  Schedule --> ShouldUpdate["shouldUpdate()"]
  ShouldUpdate --> Render["render()
lit-html diff"]
  Render --> Updated["updated()
optional hook"]

Lit reactive update cycle

What this module covers

Lesson	What you learn
Why Lit	Vanilla pain points and when Lit helps
LitElement	Reactive properties, render, scoped styles
Using in Frameworks	Drop web components into React, Vue, Angular
Distributing	npm publishing, Custom Elements Manifest, browser support

A working Lit component

Here is the simplest possible Lit element to confirm the library loads and renders correctly in the playground runner.

<lit-hello></lit-hello>