This example adds a user-editable rectangle to the map. When the user changes the bounds of the rectangle, an info window pops up displaying the new bounds.
Read the documentation.
Git and Node.js are required to run this sample locally. Follow these instructions to install Node.js and NPM. The following commands clone, install dependencies and start the sample application.
git clone -b sample-rectangle-event https://github.com/googlemaps/js-samples.git
Other samples can be tried by switching to any branch beginning with
git checkout sample-SAMPLE_NAME