ChartJS以最大值/最小值顯示工具提示

Question

我想在圖表中的數據集頂部數據點顯示工具提示。這樣用戶就可以看到最大和最小數據點的值。這有助於立即理解圖表。

應該看起來有點像這樣：

我已經在這裏創建的jsfiddle與代碼：https://jsfiddle.net/h2zscw6s/1/

僅供參考，請在下面也找到我的圖表配置。這是在咖啡腳本，但我不介意，如果你張貼在純JavaScript的答案。

dataWeather = [ 
    { 
    label: 'January' 
    value: 22 
    } 
    { 
    label: 'February' 
    value: 23 
    } 
    { 
    label: 'March' 
    value: 24 
    } 
    { 
    label: 'May' 
    value: 26 
    } 
    { 
    label: 'June' 
    value: 30 
    } 
    { 
    label: 'July' 
    value: 34 
    } 
    { 
    label: 'August' 
    value: 38 
    } 
    { 
    label: 'September' 
    value: 36 
    } 
    { 
    label: 'October' 
    value: 30 
    } 
    { 
    label: 'November' 
    value: 28 
    } 
    { 
    label: 'December' 
    value: 26 
    } 
] 
dataPrices = [ 
    { 
    label: 'January' 
    value: 5000 
    } 
    { 
    label: 'February' 
    value: 4500 
    } 
    { 
    label: 'March' 
    value: 4450 
    } 
    { 
    label: 'May' 
    value: 3700 
    } 
    { 
    label: 'June' 
    value: 3700 
    } 
    { 
    label: 'July' 
    value: 3000 
    } 
    { 
    label: 'August' 
    value: 2900 
    } 
    { 
    label: 'September' 
    value: 3100 
    } 
    { 
    label: 'October' 
    value: 3200 
    } 
    { 
    label: 'November' 
    value: 3900 
    } 
    { 
    label: 'December' 
    value: 5500 
    } 
] 

class WeatherPriceChart 
    setWeatherData: (weatherData)-> 
    @weatherData = weatherData 
    setPriceData: (priceData)-> 
    @priceData = priceData 
    minPrice: -> 
    _.sortBy(@priceData, (w)-> w.value)[0]?.value || 0 
    maxPrice: -> 
    _.sortBy(@priceData, (w)-> -w.value)[0]?.value || 0 
    minTemperature: -> 
    _.sortBy(@weatherData, (w)-> w.value)[0]?.value || 0 
    maxTemperature: -> 
    _.sortBy(@weatherData, (w)-> -w.value)[0]?.value || 0 
    isMaxTemperature: (value)-> 
    @maxTemperature() == value 
    isMinTemperature: (value)-> 
    @minTemperature() == value 
    isMaxPrice: (value)-> 
    @maxPrice() == value 
    isMinPrice: (value)-> 
    @minPrice() == value 
    getLabels: -> 
    _.map(@weatherData, (w)-> w.label) 
    getWeatherDataPoints: -> 
    _.map(@weatherData, (w)-> w.value) 
    getPriceDataPoints: -> 
    _.map(@priceData, (w)-> w.value) 
    getNormalizedWeatherDataPoints: -> 
    data = @weatherData 
    min = -10 
    max = 60 
    _.map data, (d)-> 
     norm = d.value + (min * -1) 
     maxed = max + (min * -1) 
     norm/maxed * 100 
    getNormalizedPriceDataPoints: -> 
    data = @priceData 
    max = @maxPrice() * 2.5 
    _.map data, (d)-> 
     d.value/max * 100 


chart = new WeatherPriceChart 
chart.setWeatherData(dataWeather) 
chart.setPriceData(dataPrices) 

ctx = document.getElementById('myChart') 
myChart = new Chart(ctx, 
    type: 'line', 
    data: 
    xLabels: chart.getLabels(), 
    yLabels: [""], 
    datasets: [ 
     { 
     label: 'Temperature' 
     data: chart.getWeatherDataPoints() 
     backgroundColor: 'rgba(239,88,42,0.2)' 
     borderColor: 'rgba(239,88,42,0.5)' 
     borderWidth: 1 
     }, 
     { 
     label: 'Prices' 
     data: chart.getNormalizedPriceDataPoints() 
     backgroundColor: 'rgba(22,195,245,0.2)' 
     borderColor:'rgba(22,195,245,0.4)' 
     borderWidth: 1 
     } 
    ] 
    options: 
    scales: 
     yAxes: [ 
     { 
      ticks: { 
      beginAtZero: false, 
      display: false 
      }, 
      display: false 
     }, 
     ] 
    legend: 
     display: false    
) 

Answer 1

我找到了這個選項的答案，並將其發佈到鏈接的jsfiddle中。我不得不添加一個可以顯示所有標籤的插件。那一個然後動態地決定是否顯示這個工具提示。

Chart.pluginService.register 
    beforeRender: (chart) -> 
    if chart.config.options.showAllTooltips 
     # create an array of tooltips 
     # we can't use the chart tooltip because there is only one tooltip per chart 
     chart.pluginTooltips = [] 
     chart.config.data.datasets.forEach (dataset, i) -> 
     min = _.min(dataset.data, (d)-> d) 
     max = _.max(dataset.data, (d)-> d) 
     minShown = false 
     maxShown = false 
     chart.getDatasetMeta(i).data.forEach (sector, j) -> 
      isMax = dataset.data[j] == max 
      isMin = dataset.data[j] == min 
      # only show the min and the max once. we can have duplicates min/maxes 
      if isMax && !maxShown || isMin && !minShown 
      minShown = true if isMin 
      maxShown = true if isMax 
      tooltip = new (Chart.Tooltip)({ 
       _chart: chart.chart 
       _chartInstance: chart 
       _data: chart.data 
       _options: chart.options.tooltips 
       _active: [ sector ] 
      }, chart) 
      chart.pluginTooltips.push(tooltip) 
      return 
     return 
     # turn off normal tooltips 
     chart.options.tooltips.enabled = false 
    return 
    afterDraw: (chart, easing) -> 
    if chart.config.options.showAllTooltips 
     # we don't want the permanent tooltips to animate, so don't do anything till the animation runs atleast once 
     if !chart.allTooltipsOnce 
     if easing != 1 
      return 
     chart.allTooltipsOnce = true 
     # turn on tooltips 
     chart.options.tooltips.enabled = true 
     Chart.helpers.each chart.pluginTooltips, (tooltip) -> 
     tooltip.initialize() 
     tooltip.update() 
     # we don't actually need this since we are not animating tooltips 
     tooltip.pivot() 
     tooltip.transition(easing).draw() 
     return 
     chart.options.tooltips.enabled = false 
    return