Bar Chart Race in JavaScript

var raceEntities = [
  'United States',
  'China',
  'Germany',
  'Japan',
  'France',
  'United Kingdom',
  'India',
  'Brazil',
  'Canada',
  'Italy',
]

// A fixed color per country. With distributed bars the color is applied by bar
// POSITION, but this is a race where the bars re-sort every tick, so raceFrame()
// re-orders this palette to match the current ranking below. That keeps each
// country's color stable as it rides up and down the ranks.
var raceColors = {
  'United States': '#3B82F6',
  China: '#EF4444',
  Germany: '#F59E0B',
  Japan: '#10B981',
  France: '#06B6D4',
  'United Kingdom': '#EC4899',
  India: '#14B8A6',
  Brazil: '#F97316',
  Canada: '#64748B',
  Italy: '#84CC16',
}

// A flag emoji per country, prepended to its axis label by
// yaxis.labels.formatter. SVG axis labels are plain text, so an emoji is the
// simplest way to put an icon in front of a label (real image flags would need
// custom DOM work). Emoji flags render on most platforms; a few Windows
// browsers show the two-letter country code instead.
var raceFlags = {
  'United States': '🇺🇸',
  China: '🇨🇳',
  Germany: '🇩🇪',
  Japan: '🇯🇵',
  France: '🇫🇷',
  'United Kingdom': '🇬🇧',
  India: '🇮🇳',
  Brazil: '🇧🇷',
  Canada: '🇨🇦',
  Italy: '🇮🇹',
}

// Persistent value per entity, nudged a little each tick so ranks swap
// gradually (a smooth race rather than a random shuffle).
var raceValues = {}
raceEntities.forEach(function (name, i) {
  raceValues[name] = 300 + (raceEntities.length - i) * 90
})

function raceFrame() {
  raceEntities.forEach(function (name) {
    raceValues[name] = Math.max(
      50,
      raceValues[name] + (Math.random() - 0.45) * 220,
    )
  })
  var ranked = raceEntities
    .map(function (name) {
      return { name: name, value: Math.round(raceValues[name]) }
    })
    .sort(function (a, b) {
      return b.value - a.value
    })
  return {
    categories: ranked.map(function (r) {
      return r.name
    }),
    data: ranked.map(function (r) {
      return r.value
    }),
    // Colors follow the ranking so each country keeps its own color (see above).
    colors: ranked.map(function (r) {
      return raceColors[r.name]
    }),
  }
}

var raceInitial = raceFrame()

var options = {
  series: [
    {
      name: 'Value',
      data: raceInitial.data,
    },
  ],
  chart: {
    id: 'horizontal-bar-race',
    type: 'bar',
    height: 420,
    animations: {
      dynamicAnimation: {
        speed: 800,
      },
    },
    toolbar: {
      show: false,
    },
  },
  plotOptions: {
    bar: {
      borderRadius: 4,
      borderRadiusApplication: 'end',
      horizontal: true,
      // Each bar gets its own color, taken from the `colors` palette by position.
      distributed: true,
    },
  },
  colors: raceInitial.colors,
  dataLabels: {
    enabled: true,
    // Riding to each bar's new rank is the default; counting the number up or
    // down from its previous value on every tick is the opt-in that makes it
    // read as a race.
    countUp: {
      enabled: true,
    },
  },
  title: {
    text: 'Bar Chart Race',
    align: 'left',
  },
  xaxis: {
    categories: raceInitial.categories,
  },
  yaxis: {
    labels: {
      // Prepend each country's flag emoji to its axis label.
      formatter: function (val) {
        return (raceFlags[val] || '') + '  ' + val
      },
    },
  },
  legend: {
    show: false,
  },
}

var chart = new ApexCharts(document.querySelector('#chart'), options)
chart.render()

var raceRuns = 0
var raceInterval = window.setInterval(function () {
  raceRuns++
  var frame = raceFrame()
  chart.updateOptions({
    series: [{ data: frame.data }],
    xaxis: { categories: frame.categories },
    colors: frame.colors,
  })

  if (raceRuns === 2 && window.isATest === true) {
    clearInterval(raceInterval)
  }
}, 1200)