1. EventTarget.addEventListener()

    The modern standard API for adding DOM event handlers. Introduced in the DOM Level 2 Events spec. Also implies support for `removeEventListener`, the [capture phase](https://dom.spec.whatwg.org/#dom-event-capturing_phase) of DOM event dispatch, as well as the `stopPropagation()` and `preventDefault()` event methods.

  2. regular_expressions: capturing group: `(...)`

  3. regular_expressions: named capture group: `(?<name>...)`

  4. regular_expressions: named capture group: `(?<name>...)`: duplicate names in different disjunction alternatives are allowed

  5. regular_expressions: non-capturing group: `(?:...)`