NGRX 8，angular，如何处理未定义的错误

Question

我对以下选择器有疑问：

export const selectInfoFromMap = createSelector(featureSelector, (state, props) =>
    state.attributes.get(props.userName).get(props.parameterUser).userValue);

组件初始化时，下面的地图不存在。我可以轻松检查空值。

export const selectInfoFromMap = createSelector(featureSelector, (state, props) =>
    state.attributes.get(props.userName).get(props.parameterUser).userValue ?
        state.attributes.get(props.userName).get(props.parameterUser).userValue : '0.0');

但是，是否可以检查 undefined？

Answer 1

这是对属性的深入挖掘，你最好使用 try catch

export const selectInfoFromMap = createSelector(featureSelector, (state, props) =>{

   try{ 
      return state.attributes.get(props.userName).get(props.parameterUser).userValue
    }catch(e){
        return '0.0'
}

NGRX 8，angular，如何处理未定义的错误

NGRX 8, angular, how to handle undefined error

angular

typescript

rxjs

ngrx

ngrx-store