Mobx4-声明存储中的可观察项引发sintax错误

根据 migration guide from mobx ,这是现在分配观测值的正确方法(即 ... 代表其他无关代码):

class BaseMapsStore {
  uiStore = null
  mapStore = null
  datesStore = null
  selectedBaseMap = "OSM"
  baseMapOptions = ["Sentinel", "OSM", "None"]
  layers = null
  ...
}

export default decorate(BaseMapsStore, {
  uiStore: observable,
  mapStore: observable,
  datesStore: observable,
  selectedBaseMap: observable,
  baseMapOptions: observable,
  layers: observable,
  ...
});

但使用create react应用程序时,我遇到以下错误: 未能编译。

未能编译。

./src/stores/BaseMapsStore/BaseMapsStore.js
Syntax error: Unexpected token (12:10)

  10 | 
  11 | class BaseMapsStore {
> 12 |   uiStore = null
     |           ^
  13 |   mapStore = null
  14 |   datesStore = null
  15 |   selectedBaseMap = "OSM"

我需要一个巴别塔插件,以使这项工作?确切的语法错误是什么?