Directory search widget streamfield block has a location autocomplete field.
The HTML template of the block can be found at bc/project_styleguide/templates/patterns/molecules/location-autocomplete/location-autocomplete.html.
The JavaScript component can be found at bc/static_src/javascript/components/location-autocomplete.js.
It uses Google Maps API to provide location suggestions: https://developers.google.com/maps/documentation/javascript/reference/places-autocomplete-service
It requires the GOOGLE_MAPS_V3_APIKEY environment variable to be configured. This settings is also used by different components on the website (e.g. location maps widget).