[Chartjs]-Bold text inside doughnut chart (chart.js)

Plz see HTML canvas font Property.

The JavaScript syntax: context.font=”italic small-caps bold 12px arial”;

Reference: https://www.w3schools.com/tags/canvas_font.asp

In your case just replace:

let ctx           =   chart.chart.ctx;
let fontSize      =   (height / 100).toFixed(2);

ctx.textAlign     =   'center';
ctx.textBaseline  =   'middle';
ctx.font          =   "bold " + fontSize + "em Montserrat";