Bundle all CSS fonts as Promises

load-fonts-as-promises.js

function loadFonts() {
  if ("fonts" in document) {
    var font = new FontFace(
      "Noto Serif",
      "url(notoserif.woff2) format('woff2'), url(notoserif.woff) format('woff')"
    );

    var fontBold = new FontFace(
      "Noto Serif",
      "url(notoserif-bold.woff2) format('woff2'), url(notoserif-bold.woff) format('woff')",
      { weight: "700" }
    );

    Promise.all([
      font.load(),
      fontBold.load()
    ]).then(function(loadedFonts) {

      // Render them at the same time
      loadedFonts.forEach(function(font) {
        document.fonts.add(font);
      });
    });
  }
}

if( navigator.connection && navigator.connection.saveData ) {
} else {
  loadFonts();
}