this.checkProvince = this.region.province?.province || ''

This code uses optional chaining to access the `province` property of the `region` object. If `region` is `undefined` or `null`, the expression will short-circuit and return `undefined`. If `region` is defined, but `province` property is not defined, the expression will also return `undefined`.

If `province` property is defined in `region` object, it will return the value of `province` property. If the value of `province` is falsy (e.g. an empty string), it will return an empty string as a default value.

The result of this expression is then assigned to the `checkProvince` variable.