Function.prototype.catch = function(callback) {
  const f = this;
  return function(...args) {
    try {
      const v = f.apply(this, args);
      if ('then' in v && 'catch' in v) {
        return v.catch(callback);
      }
      return v;
    } catch (err) {
      return callback(err);
    }
  }
}