可选链

TypeScript 3.7 版本已实现了此功能

{
  // before
  const street = user && user.address && user.address.street;
  const num =    user && user.address && user.address.getNum && user.address.getNum();
  const arr = user && user.address && user.address.dataList && user.address.dataList[0] && user.address.dataList[0].details;
  console.log(street, num);
}
{
  // now
  const street2 = user?.address?.street;
  const num2 = user?.address?.getNum?.();
  const arr2 = user?.address?.dataList?.[0]?.details;
  console.log(street2, num2);
}