Create a scale-dependent visualization

This sample demonstrates how to create a scale-dependent visualization with a HeatmapRenderer and a SimpleRenderer.

A HeatmapRenderer is ideal for visualizing large, dense point datasets, particularly those that have lots of overlapping points. However, the heatmap is only effective at certain scales. It particularly tends to fail to convey useful information at large scales.

You can setup a watch on the view's scale property and set a scale threshold where the layer's renderer can switch from a heatmap to discrete marker symbols as the user zooms to large scales.

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        view.when().then(() => {
          // When the view is ready, clone the heatmap renderer
          // from the only layer in the web map

          const layer = view.map.layers.getItemAt(0);
          const heatmapRenderer = layer.renderer.clone();

          // The following simple renderer will render all points as simple
          // markers at certain scales
          const simpleRenderer = {
            type: "simple",
            symbol: {
              type: "simple-marker",
              color: "#c80000",
              size: 5
            }
          };

          // When the scale is larger than 1:72,224 (zoomed in passed that scale),
          // then switch from a heatmap renderer to a simple renderer. When zoomed
          // out beyond that scale, switch back to the heatmap renderer
          reactiveUtils.watch(
            () => view.scale,
            (scale) => {
              layer.renderer = scale <= 72224 ? simpleRenderer : heatmapRenderer;
            }
          );
        });