Object.prototype._assign_ = function (target, ...sources) {
  if (target === null) {
    throw new TypeError('Cannot convert undefined or null to object');
  }
  const to = Object(target);
  for (const source of sources) {
    if (source !== null) {
      for (const key in source) {
        if (Object.hasOwnProperty.call(source, key)) {
          to[key] = source[key];
        }
      }
    }
  }
  return to;
};
// test
const res = Object._assign_({}, 's', { a: 2 });
console.log(res);