I am a GISer!
The first map is a basic application of leaflet. I download the shapefile data and convert it to the geojson format in QGIS. And then I use the leaflet to publish the map and customize the style.
The second map is based on the first one. It is a map of properties. You can click the points to get the information of them
The third map shows the population density in China. I download the population data from the China census bureau and use the leaflet to publish the result.