[Chartjs]-Chart.js v2: How to make tooltips always appear on line chart?

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When using the latest stable version of Chart.js (2.9.3), it works with the following changes.

  1. Instead of Chart.pluginService.register, use Chart.plugin.register
  2. Instead of change _options : chart.options write _options : chart.options.tooltips

Please have a look at your amended code below.

Chart.plugins.register({
  beforeRender: function(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(function(dataset, i) {
        chart.getDatasetMeta(i).data.forEach(function(sector, j) {
          chart.pluginTooltips.push(new Chart.Tooltip({
            _chart: chart.chart,
            _chartInstance: chart,
            _data: chart.data,
            _options: chart.options.tooltips,
            _active: [sector]
          }, chart));
        });
      });      
      chart.options.tooltips.enabled = false; // turn off normal tooltips
    }
  },
  afterDraw: function(chart, easing) {
    if (chart.config.options.showAllTooltips) {
      if (!chart.allTooltipsOnce) {
        if (easing !== 1) {
          return;
        }
        chart.allTooltipsOnce = true;
      }
      chart.options.tooltips.enabled = true;
      Chart.helpers.each(chart.pluginTooltips, function(tooltip) {
        tooltip.initialize();
        tooltip.update();
        tooltip.pivot();
        tooltip.transition(easing).draw();
      });
      chart.options.tooltips.enabled = false;
    }
  }
});

new Chart("chart", {
  type: 'line',
  data: {
    labels: ["January", "February", "March", "April", "May", "June", "July"],
    datasets: [{
      label: "My First dataset",
      fillColor: "rgba(220,220,220,0.2)",
      strokeColor: "rgba(220,220,220,1)",
      pointColor: "rgba(220,220,220,1)",
      pointStrokeColor: "#fff",
      pointHighlightFill: "#fff",
      pointHighlightStroke: "rgba(220,220,220,1)",
      data: [65, 59, 80, 81, 56, 55, 40]
    }]
  },
  options: {
    scales: {
      yAxes: [{
        ticks: {
          beginAtZero: true
        }
      }]
    },
    showAllTooltips: true
  }
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.3/Chart.min.js"></script>
<canvas id="chart" height="100"></canvas>

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