Recommend return type annotation (#1239) (#415)
Recommend return type annotation (#1239) (#415)

* Recommend return type annotation (#1239)

* Recommend return type annotation

* make explanation clear, thank @DanielRosenwasser

* translate

* update date

vuejs/jp.vuejs.org,potato4d/jp.vuejs.org,potato4d/jp.vuejs.org,vuejs/jp.vuejs.org