code: function fontFamily(val) {
          if (Array.isArray(val)) {
              return val.map(fontFamily).join(",");
          } else if (typeof val === "object") {
              injectStyleOnce(val.fontFamily, "@font-face", [val], false);
              return '"' + val.fontFamily + '"';
          } else {
              return val;
          }
      }
docs: With fontFamily we look for objects that are passed in and interpret them as @font-face rules that we need to inject. The value of fontFamily can either be a string (as normal), an object (a single font face), or an array of objects and strings.