本课内容目前为英文。
This or that
Real values are not always one type. An id can be a string or a number; a lookup can find a user or return null. A union type lists every possibility, and TypeScript makes sure you handle each one.
本课内容目前为英文。
Real values are not always one type. An id can be a string or a number; a lookup can find a user or return null. A union type lists every possibility, and TypeScript makes sure you handle each one.