Build a chart.js config as string with function substitution

example.js

const chartObj = {
  type: 'bar',
  data: {
    labels: ['January', 'February', 'March', 'April', 'May'],
    datasets: [{
      label: 'Dogs',
      data: [ 50, 60, 70, 180, 190 ]
    }]
  },
  options: {
    scales: {
      yAxes: [{
        ticks: {
          callback: '{{CALLBACK_PLACEHOLDER}}',
        }
      }],
    },
  },
};

const myFormatterFunction = function(value) { 
  return "$" + value 
};
const chartStr = JSON.stringify(chartObj).replace('"{{CALLBACK_PLACEHOLDER}}"', myFormatterFunction.toString());

console.log(encodeURIComponent(chartStr));