I am using Airship and carto-vl while working through this tutorial and the values in the widget are coming back as NaN. Here is my code:

<!DOCTYPE html>

  <!-- Include CSS elements -->
  <link rel="stylesheet" href="https://libs.cartocdn.com/airship-style/v1.0.3/airship.css">
  <!-- Include icons -->
  <link rel="stylesheet" href="https://libs.cartocdn.com/airship-icons/v1.0.3/icons.css">
  <!-- Include airship components -->
  <script src="https://libs.cartocdn.com/airship-components/v1.0.3/airship.js"></script>
  <!-- Include Mapbox GL JS -->
  <script src="https://libs.cartocdn.com/mapbox-gl/v0.48.0-carto1/mapbox-gl.js"></script>
  <!-- Include Mapbox GL CSS -->
  <link href="https://libs.cartocdn.com/mapbox-gl/v0.48.0-carto1/mapbox-gl.css" rel="stylesheet" />
  <!-- Include CARTO VL JS -->
  <script src="https://libs.cartocdn.com/carto-vl/v1.1.1/carto-vl.min.js"></script>
  <title>Airship Testing</title>

<body class="as-app-body">
  <div class="as-app">
    <div class="as-content">
      <main class="as-main">
        <div class="as-map-area">
          <div id="map"></div>
      <aside class="as-sidebar as-sidebar--right">
        <as-category-widget id="cities-widget" heading="Populated places" description="Maximun population of the most pouplated cities">

  <!-- CARTO basemap -->
    const map = new mapboxgl.Map({
      container: 'map',
      style: 'https://basemaps.cartocdn.com/gl/voyager-gl-style/style.json',
      center: [0, 30],
      zoom: 2,
      scrollZoom: true,
      dragRotate: false,
      touchZoomRotate: false

    // Define user
      user: 'cartovl',
      apiKey: 'default_public'

    // Define layer
    const source = new carto.source.Dataset('ne_10m_populated_places_simple');
    const viz = new carto.Viz(`
      @cities: viewportFeatures($pop_max, $name)
    const layer = new carto.Layer('layer', source, viz);

    const $categoryWidget = document.querySelector('#cities-widget');

    function updateWidgets() {
      $categoryWidget.categories = viz.variables.cities.value
        .map(feature => ({
          name: feature.name,
          value: feature.pop_max,
        .sort((a, b) => b.value - a.value);


    layer.on('updated', updateWidgets);
    layer.addTo(map, 'watername_ocean');


Here is what the app looks like:

carto page

Why are the values of the table not returning?

I thought there might be a bug in the tutorial, but I transferred the same methodologies over to a personal project and I got the same results.


As you mention, the tutorial has a mistake. You're not getting the properties from the feature in the loop correctly. The code from the example is:

$categoryWidget.categories = viz.variables.cities.value
  .map(feature => ({
    name: feature.name,
    value: feature.pop_max,
  .sort((a, b) => b.value - a.value);

This is wrong. If you take a look to the feature object in the loop, you'll see that the nameand pop_max are not in the feature, but in the feature.properties. Therefore, the correct code is:

$categoryWidget.categories = viz.variables.cities.value
  .map(feature => ({
    name: feature.properties.name,
    value: feature.properties.pop_max,
  .sort((a, b) => b.value - a.value);

working example

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