A callback function defining the new format for the label of the Progress Bar.
Code examples
Set the formatFunction property.
let circularProgressBar = document.querySelector('jqx-circular-progress-bar');
circularProgressBar.formatFunction = function(value) { return "$" + value };
Get the formatFunction property.
let circularProgressBar = document.querySelector('jqx-circular-progress-bar');
let formatFunction = circularProgressBar.formatFunction;