groupBy based on range of values using RxJS in angular

I have a raw data array

[ {bugid: b1 , state: 'foo', days: 2}, {bugid: b2, state: 'bar', days: 41}, {bugid: b3, state: 'foo', days: 45} ]

I want to group this data using RxJS in this format

{ '0-25': [{ name: foo, value: 1}, {name: bar, value: 0}], '26-50': [{name: foo, value: 1}, {name: bar, value: 1}] }

I am not able to group in the range