Replacing Nested Switch Statements with Objects

I came across a scenario in which I had to use nested switch statements to return values based on nested cases. Although easy to implement using nested switch cases was not convincing enough for me considering the performance.
My code looked like the below function:

The function converts array indexes into minutes based on hour parameter named "hourGranularity.

function replaceMinuteIndexInMinutes(hourGranularity, index) {

 

    switch (hourGranularity) {

 

        case 1:

            {

                switch (index) {

                    case 0:

                        return 0;

                    default:

                        return null;

                }

            }

        case 2:

            {

                switch (index) {

                    case 0:

                        return 0;

                    case 1:

                        return 30;

                    default:

                        return null;

                }

            }

        case 4:

            {

                switch (index) {

                    case 0:

                        return 0;

                    case 1:

                        return 15;

                    case 2:

                        return 30;

                    case 3:

                        return 45;

                    default:

                        return null;

                }

            }

        default:

            {

                return 0;

            }

    }

 

}

The above function looks great but can prove to be a performance nightmare, So, A better way to achieve the desired result using such static values is using object literals. The approach uses multidimensional arrays/objects which involves taking each case as an index/key and returning the value for the corresponding matrix formed. For Instance:

function replaceMinuteIndexInMinutes(hourGranularity, index) {

let minuteIndexInMinutesObj = {

1:

{

0: 0

},

2:

{

0: 0,

1: 30,

},

4:

{ 

0: 0,

1: 15,

2: 30,

3: 45,

},

}

return minuteIndexInMinutesObj[hourGranularity][index]

 

}

Thanks.