$ show googlemaps/js-markerclusterer
This repository provides the `@googlemaps/markerclusterer` library, a TypeScript/JavaScript package for clustering large numbers of markers on Google Maps. The core `MarkerClusterer` class extends `google.maps.OverlayView` and orchestrates a pluggable pipeline: an `Algorithm` (default: SuperCluster) groups markers into `Cluster` objects, and a `Renderer` (default: SVG circles) visualizes them. It supports both legacy `google.maps.Marker` and modern `AdvancedMarkerElement`. The library is distributed as an npm package (UMD, ESM, IIFE) and includes examples with real-world coordinate data. External dependencies include the Google Maps JavaScript API runtime, the `supercluster` library for spatial indexing, and `@googlemaps/jest-mocks` for testing. The architecture emphasizes extensibility through well-defined interfaces, making it suitable for integration into larger mapping applications.
The LLM identified 4 files worth highlighting for reuse:
Provides a unified interface for interacting with both legacy `google.maps.Marker` and modern `AdvancedMarkerElement`. Functions like `getPosition`, `setMap`, and `getVisible` abstract away the differences in API (e.g., `getPosition()` vs `.position`). This pattern is reusable for any Google Maps library that needs to support both marker types without coupling to the specific implementation.
Defines the abstract `Algorithm` interface and the `AlgorithmInput` type. This is the core of the pluggable clustering strategy. Any custom algorithm (e.g., grid-based, viewport-filtered) can implement this interface and be injected into `MarkerClusterer`. The file also includes the `noop` algorithm as a trivial default. This pattern is a clean example of the Strategy pattern for algorithm selection.
Defines the `Renderer` interface and provides a `DefaultRenderer` that creates SVG circle markers with cluster counts. The interface is minimal (`render` method returning a marker), allowing custom renderers (e.g., using custom icons, HTML elements) to be swapped in. This separation of concerns between clustering logic and visual representation is a strong architectural pattern.
Contains reusable test utilities for Google Maps JavaScript API mocking: `initializeMocks()` sets up global `google.maps` objects, `setupMapBounds()` configures map bounds, and `testMarkerTypes` parameterizes tests for both legacy and advanced markers. This pattern can be extracted and reused in any project that needs to test Google Maps components without a real browser environment.