如何在chartjs中显示百分比符号？

var chartOptions = {
  tooltips: {
    callbacks: {
      label: function(tooltipItem, data) {
        var dataset = data.datasets[tooltipItem.datasetIndex];
        var value = dataset.data[tooltipItem.index];
        var total = dataset.data.reduce(function(previousValue, currentValue) {
          return previousValue + currentValue;
        });
        var percentage = ((value / total) * 100).toFixed(2) + "%";
        return dataset.label + ": " + percentage;
      }
    }
  }
};

var chartData = {
  labels: ["A", "B", "C"],
  datasets: [{
    data: [30, 50, 20],
    label: "数据集"
  }]
};

var ctx = document.getElementById("myChart").getContext("2d");
var myChart = new Chart(ctx, {
  type: "pie",
  data: chartData,
  options: chartOptions
});