Chartjs-Can not read property 'Concat' of Undefined

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You would have to set the chart type in the main chart option, not inside the dataset (the second one) :

var chart = new Chart(ctx, {
   type: 'bar',
   data: {
      ...

Here is the working version of your code :

var labelsarr = ['A', 'B', 'C'];
var linedata = [2, 5, 3];
var bardata = [4, 2, 6];

var ctx = document.getElementById('canvas').getContext('2d');
var chart = new Chart(ctx, {
   type: 'bar', //<-- set here
   data: {
      labels: labelsarr,
      datasets: [{
         type: 'line',
         fill: false,
         label: 'Line Example',
         backgroundColor: 'rgba(255,0,0,1)',
         borderColor: 'rgba(255,0,0,1)',
         data: linedata

      }, {
         label: 'Bar Example',
         backgroundColor: 'rgba(0, 129, 214, 0.8)',
         data: bardata
      }]
   },
   options: {
      tooltips: {
         callbacks: {
            label: function(t, d) {
               var xLabel = d.datasets[t.datasetIndex].label;
               var yLabel = t.yLabel >= 1000 ? '$' + t.yLabel.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",") : '$' + t.yLabel;
               return xLabel + ': ' + yLabel;
            }
         }
      },
      legend: {
         display: false,
         position: 'top',
      },
      scales: {
         yAxes: [{
            ticks: {
               beginAtZero: true,
               callback: function(value, index, values) {
                  if (parseInt(value) >= 1000) {
                     return '$' + value.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
                  } else {
                     return '$' + value;
                  }
               }
            }
         }]
      }
   },
   plugins: [{
      beforeDraw: function(chart) {
         var labels = chart.data.labels;
      }
   }]
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.6.0/Chart.min.js"></script>
<canvas id="canvas"></canvas>

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