Drill-Down Map

// Create root element
// https://docs.amcharts.com/v5/getting-started/#root-element
var root = am5.Root.new("chartdiv");

// Set themes
// https://docs.amcharts.com/v5/concepts/themes/
root.setThemes([
  am5themes_Animated.new(root),
  am5themes_Responsive.new(root)
]);

// Create the map chart
// https://docs.amcharts.com/v5/charts/map-chart/
var chart = root.container.children.push(am5map.MapChart.new(root, {
  minZoomLevel: 0.5,                 // zoom out to half the fitted size at most
  // go to the home view once the map is fitted
  autoHome: true,
  panX: "rotateX",                   // dragging sideways turns the world, so the map wraps around
  projection: am5map.geoEqualEarth() // a world map that keeps the countries' areas true to size
}));

// Zoom control, at the bottom right, away from the house button
// https://docs.amcharts.com/v5/charts/map-chart/map-pan-zoom/#zoom-control
var zoomControl = chart.set("zoomControl", am5map.ZoomControl.new(root, {}));

// the home button is hidden by default
zoomControl.homeButton.set("visible", true);

// Create series for the water: a faint fill behind the countries
// https://docs.amcharts.com/v5/charts/map-chart/map-polygon-series/#background-polygon
var waterSeries = chart.series.push(am5map.MapPolygonSeries.new(root, {
  // the map fits the countries, not this rectangle around the whole world
  affectsBounds: false
}));

waterSeries.mapPolygons.template.setAll({
  fill: root.interfaceColors.get("alternativeBackground"), // dark on a light background, light on a dark one
  fillOpacity: 0.05, // barely there
  strokeOpacity: 0   // no outline
});

waterSeries.data.push({
  geometry: am5map.getGeoRectangle(90, 180, -90, -180) // north, east, south and west edges: the whole world
});

// Create graticule series: grid lines every 10 degrees
// https://docs.amcharts.com/v5/charts/map-chart/graticule-series/
var graticuleSeries = chart.series.push(am5map.GraticuleSeries.new(root, {
  step: 10
}));

graticuleSeries.mapLines.template.setAll({
  stroke: root.interfaceColors.get("alternativeBackground"), // dark on a light background, light on a dark one
  strokeOpacity: 0.08 // very faint
});

// Create polygon series for continents
// https://docs.amcharts.com/v5/charts/map-chart/map-polygon-series/
var continentSeries = chart.series.push(am5map.MapPolygonSeries.new(root, {
  geoJSON: am5geodata_continentsLow
}));

continentSeries.mapPolygons.template.setAll({
  tooltipText: "{name}", // the continent's name on hover
  interactive: true      // reacts to hover and clicks
});

continentSeries.mapPolygons.template.states.create("hover", {
  fill: root.interfaceColors.get("primaryButtonActive") // the hovered continent takes the theme's button color
});

// Set up zooming in on clicked continent
continentSeries.mapPolygons.template.events.on("click", function (ev) {
  continentSeries.zoomToDataItem(ev.target.dataItem); // zoom in to fit the clicked continent...
  continentSeries.hide(); // ...swap the continents...
  countrySeries.show();   // ...for its countries
  homeButton.show();      // and show the way back
});

// Create polygon series for countries
// https://docs.amcharts.com/v5/charts/map-chart/map-polygon-series/
var countrySeries = chart.series.push(am5map.MapPolygonSeries.new(root, {
  geoJSON: am5geodata_worldLow,
  visible: false // hidden until a continent is clicked
}));

countrySeries.mapPolygons.template.setAll({
  tooltipText: "{name}", // the country's name on hover
  interactive: true      // reacts to hover
});

countrySeries.mapPolygons.template.states.create("hover", {
  fill: root.interfaceColors.get("primaryButtonActive")
});

// Add a button to go back to continents view
var homeButton = chart.children.push(am5.Button.new(root, {
  paddingTop: 10,            // 10px above and below the icon
  paddingBottom: 10,
  x: am5.percent(100),       // at the chart's right edge...
  centerX: am5.percent(100), // ...aligned by its own right edge
  visible: false,            // hidden until a continent is clicked
  // the button takes the click itself, not its icon
  interactiveChildren: false,
  icon: am5.Graphics.new(root, {
    // a house icon, as SVG path data
    svgPath: "M16,8 L14,8 L14,16 L10,16 L10,10 L6,10 L6,16 L2,16 L2,8 L0,8 L8,0 L16,8 Z M16,8",
    fill: am5.color(0xffffff) // a white icon
  })
}));

// back to the continents: zoom out and swap the countries for the continents
function goBack() {
  chart.goHome();
  continentSeries.show();
  countrySeries.hide();
  homeButton.hide();
}

homeButton.events.on("click", goBack);

// the zoom control's home button goes back to the continents too
zoomControl.homeButton.events.on("click", goBack);