function getRenderedFontFamily(fontFamily) {
  let f = ''
  let canvas = document.createElement("canvas");
  let context = canvas.getContext("2d");
  let families = fontFamily.split(',');

  for(let family of families) {
    if (family == 'inherit') {
      f = family;
    }
    let text = "abcdefghijklmnopqrstuvwxyz";

    context.font = "1000px " + family + ", serif";
    let serifWidth = context.measureText(text).width;

    context.font = "1000px " + family;
    let width1 = context.measureText(text).width;

    context.font = "1000px " + family + ", sans-serif";
    let sansWidth = context.measureText(text).width;

    context.font = "1000px " + family;
    let width2 = context.measureText(text).width;
 
    if (serifWidth == width1 && sansWidth == width2) {
      f = family
    }
  }
      
  return f;
}

 const fonts = {}
 const elements = document.body.getElementsByTagName("*");
 [...elements].map(element => {
     element.focus();
     const font = getRenderedFontFamily(window.getComputedStyle(element).getPropertyValue("font-family"));
     fonts[font] = 0
 })
 console.log(Object.keys(fonts).join('\n'))