Sample lambda demonstrating how to render an image using ChartJS

ChartJSLambda.js

'user strict';

const debug = require('debug');
const { CanvasRenderService } = require('chartjs-node-canvas');
const fs = require('fs');

// bug workaround: https://github.com/vmpowerio/chartjs-node/issues/26
if (global.CanvasGradient === undefined) {
  global.CanvasGradient = function() {};
}

async function renderChartWithChartJS() {
  const width = 400;
  const height = 400;
  const configuration = {
      type: 'bar',
      data: {
          labels: ['Red', 'Blue', 'Yellow', 'Green', 'Purple', 'Orange'],
          datasets: [{
              label: '# of Votes',
              data: [12, 19, 3, 5, 2, 3],
              backgroundColor: [
                  'rgba(255, 99, 132, 0.2)',
                  'rgba(54, 162, 235, 0.2)',
                  'rgba(255, 206, 86, 0.2)',
                  'rgba(75, 192, 192, 0.2)',
                  'rgba(153, 102, 255, 0.2)',
                  'rgba(255, 159, 64, 0.2)'
              ],
              borderColor: [
                  'rgba(255,99,132,1)',
                  'rgba(54, 162, 235, 1)',
                  'rgba(255, 206, 86, 1)',
                  'rgba(75, 192, 192, 1)',
                  'rgba(153, 102, 255, 1)',
                  'rgba(255, 159, 64, 1)'
              ],
              borderWidth: 1
          }]
      },
      options: {
          scales: {
              yAxes: [{
                  ticks: {
                      beginAtZero: true,
                      callback: (value) => '$' + value
                  }
              }]
          }
      }
  };
  const chartCallback = (ChartJS) => {
      ChartJS.defaults.global.responsive = true;
      ChartJS.defaults.global.maintainAspectRatio = false;
  };

  debug("Rendering chart");
  const canvasRenderService = new CanvasRenderService(width, height, chartCallback);
  return await canvasRenderService.renderToBuffer(configuration);
}

module.exports.renderChart = async function(event, context, callback) {
  const buffer = await renderChartWithChartJS();
  fs.writeFileSync('/tmp/chartjs-test.png', buffer);

  const response = {
    statusCode: 200,
    body: null
  };

  callback(null, response);
}