1. CSS namespaces

    Using the `@namespace` at-rule, elements of other namespaces (e.g. SVG) can be targeted using the pipe (`|`) selector.

  2. attr api: namespaceuri

  3. cssnamespacerule api

  4. cssnamespacerule api: namespaceuri

  5. cssnamespacerule api: prefix

  6. element api: getelementsbytagnamens: `getelementsbytagnamens(namespaceuri, "*")`

  7. element api: namespaceuri

  8. mutationrecord api: attributenamespace

  9. node api: isdefaultnamespace

  10. node api: lookupnamespaceuri

  11. css selector: namespace selector (`|`)

  12. css selector: type selector (`elementname`): namespaces (`ns|elementname`)

  13. css selector: universal selector (`*`): namespaces (`*|*`)

  14. javascript statement: export: `export * as namespace`

  15. global_attributes: requiredextensions: recognizes mathml namespace

  16. ecmascript 2020 (es11)