[Solved]-How to get data from Api first and then call the my function?-Reactjs

There are some issues in your code

1. setState may be asynchronous, meaning state wont get updated immediately after setState is call. It is mentioned clearly in React docs: https://reactjs.org/docs/state-and-lifecycle.html#state-updates-may-be-asynchronous
2. You should never directly modify the state inside componentDidMount It is also mentioned here: https://reactjs.org/docs/state-and-lifecycle.html#do-not-modify-state-directly So I suggest modify the code as below

    componentDidMount() {
      this.getDeductionInfosList(data, function(response){
        this.createAppState({
            group: [{ field: "DeductionTypeTitle" }]}, response.Result, true)
      });
    }
    createAppState(dataState, items collapseAll) {
      const dataResult = process( items, dataState);
      if (collapseAll) {
        dataResult.data.forEach(dataItem => dataItem.expanded = false);
      }
      this.setState({
        dataResult: dataResult,
        dataState: dataState 
      });
    }