vendors/tempy.js/f
    function onceStrict(fn) {
      var f = function() {
        if (f.called)
          throw new Error(f.onceError);
        f.called = true;
        return f.value = fn.apply(this, arguments);
      };
      var name = fn.name || "Function wrapped with `once`";
      f.onceError = name + " shouldn't be called more than once";
      f.called = false;
      return f;
    }