examples-3.x-dev/modules/js_example/js_example.routing.yml

js_example.info:
  path: '/examples/js-example'
  defaults:
    _title: 'JavaScript Example information'
    _controller: '\Drupal\js_example\Controller\JsExampleController::description'
  requirements:
    _permission: 'access content'

js_example.colors:
  path: '/examples/js-example/colors'
  defaults:
    _title: 'JavaScript Example: Weighting in action'
    _controller: '\Drupal\js_example\Controller\JsExampleController::showColors'
  requirements:
    _permission: 'access content'

js_example.accordion:
  path: '/examples/js-example/accordion'
  defaults:
    _title: 'JavaScript Example: Accordion'
    _controller: '\Drupal\js_example\Controller\JsExampleController::showAccordion'
  requirements:
    _permission: 'access content'