Chartjs-Bar chart labels in Chart.JS

as described in the documentation you need to register the plugin first

//Global register
Chart.register(ChartDataLabels);

//Per chart registration
var chart = new Chart(ctx, {
  plugins: [ChartDataLabels],
  type: 'line',
  data: {
    // ...
  },
  options: {
    // ...
  }
})