State

A part with state has one prop for it, such as isSelected of a Checkbox or value of a TextField. How you pass it picks who keeps the state.

<!-- The part keeps its own state, which starts off. -->
<Checkbox>Subscribe</Checkbox>

<!-- The part keeps its own copy, which starts on. A new value from you replaces it. -->
<Checkbox isSelected>Subscribe</Checkbox>

<!-- The part writes your signal. -->
<Checkbox isSelected=$bind(subscribed)>Subscribe</Checkbox>

<!-- The part asks you. It shows what you keep. -->
<Checkbox isSelected=$bind(subscribed, (next) => { if (!locked) subscribed = next; })>Subscribe</Checkbox>

• Each part also calls onChange with the new value, in every shape.
• A value of null is a value like any other, such as the value of a RadioGroup with nothing chosen.
• On the server, nothing writes, so every shape renders the value that it starts with.

There is no defaultSelected or defaultValue: a let prop of brumate already does both. See Props that the component writes.