Ensures a container element has an id, generating one when missing.
MAIDR resolves a chart's selectors inside that chart, so a bare selector like
"rect.bar" does not reach another chart's marks there. Stamping the
container with a stable id and prefixing emitted selectors with #<id>
makes each selector name this chart's marks alone wherever it is read,
without requiring users to set the id themselves.
Idempotent: re-calling on a container that already has an id is a no-op.
Parameters
container: Element
The root container element (or any element).
prefix: string = 'maidr'
Adapter-specific id prefix used when generating a new id.
Ensures a container element has an
id, generating one when missing.MAIDR resolves a chart's selectors inside that chart, so a bare selector like
"rect.bar"does not reach another chart's marks there. Stamping the container with a stable id and prefixing emitted selectors with#<id>makes each selector name this chart's marks alone wherever it is read, without requiring users to set the id themselves.Idempotent: re-calling on a container that already has an id is a no-op.