dateRangePicker: {
             selection: {
              startDate: new Date(),
              endDate: new Date(),
              key: 'selection',
            },

let startDate = "2019-04-16";
  let endDate = "2019-05-16";

this.setState({
    dateRangePicker.selection.startDate : startDate,
    dateRangePicker.selection.endDate : endDate,
  })