Overview
The Maps JavaScript API uses libraries to provide supplemental
features. The visualization library includes the
HeatmapLayer class, which you can use to visualize data
intensity at geographical points.
For example, the earthquake mapping tutorial uses the HeatMapLayer
class to plot earthquake locations and intensity, and walks you step by step
through the code.
Using the library
The visualization library is a self-contained library, separate from the main
Maps JavaScript API code. To use the functionality contained within
this library, you must first load it using the libraries parameter in the
Maps JavaScript API bootstrap URL:
<script src="https://maps.googleapis.com/maps/api/js?libraries=visualization"></script>