Glossary

Action

An HTML attribute such as data-herb-toggle that writes a state when an event fires. See Actions.

Binding

A state: option on a render call that makes a partial's state and a state of the caller one state. See Binding a partial's state.

Collection

A loop in a template compiled with slots. Its rows are matched across updates by their key. See Keys and collections.

Component

One of the built-in capitalized tags <Fragment>, <Async>, <Lazy> and <Fallback>, which compile into ordinary HTML and slots. See Components.

Derived state

A state whose default reads other states, such as busy: pending || failed. The client recomputes it whenever one of those changes, and nothing can write it. See Derived states.

Diagnostic

A finding about a template, with a location, a message and often a suggestion. Parse errors, engine validators and linter rules all produce diagnostics.

Directive

An ERB comment that Herb reads as an instruction, such as <%# herb:state (...) %>, <%# herb:key ... %> or <%# herb:slots %>. Any other ERB engine sees an ordinary comment.

ERB tag

A Ruby tag inside a template, such as <% %>, <%= %> or <%# %>. See ERB tags.

Fallback

The markup a component shows while its content is stale or still loading. See <Fallback>.

HTML+ERB

HTML with embedded Ruby, read as one language where elements, attributes and ERB tags belong to the same tree. Plain ERB treats the HTML as text. See Templates.

Key

The value that identifies a row in a collection, given with <%# herb:key %>, a herb-key attribute or a dynamic id. See herb:key.

Kind

The type of value a state holds, decided by its default. The kinds are Boolean, Integer, String, Symbol, Nil and Seeded. See Kinds.

Overlay

The panel ReActionView shows on the page in development when a template has an error, in place of a stack trace.

Parser option

A setting that changes how the parser reads a template, such as strict or html. See Parser options.

Region

One rendering of one template in the page, marked by herb-region comments. A partial rendered three times makes three regions.

Scoped style

A <style scoped> block whose CSS applies only to the markup in the same file. See Scoped styles.

Slot

A place in the rendered page that holds something dynamic, marked so the client can find it and update only that part. See Slots.

State

A value the browser owns, declared with <%# herb:state (...) %>. The server renders it with its default, and the client updates every part of the page that reads it. See State.

Strict locals

A Rails magic comment, <%# locals: (...) %>, that declares which locals a partial takes. See Strict locals.

Syntax tree

The structure the parser builds from a template, with a node for every element, attribute, text and ERB tag. Every Herb tool works on it.