How do I extract only the KEYS from an array of objects?

How do I extract only the time range KEYS within an array of objects?

The following is my code:

console.log(tempRemovedTimeRanges);

const removedKeys = tempRemovedTimeRanges
  .flatMap(obj => Object.values(obj))
  .filter(dayArray => dayArray.some(dayObj => Object.keys(dayObj)[0] === elementToInsert))
  .flatMap(dayArray =>
    dayArray
      .filter(dayObj => Object.keys(dayObj)[0] === elementToInsert)
      .flatMap(dayObj => dayObj[elementToInsert].flatMap(range => Object.keys(range)))
  );

console.log(removedKeys);

The code above logs out:

(8) [{…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}]
[]

As you can see the console.log(removedKeys); code logs out an empty array.

Allow me to expand tempRemovedTimeRanges array for you to get an idea of the tempRemovedTimeRanges structure:

(8) [{…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}]
   0: {Wednesdays: Array(2)}
   1: {Fridays: Array(2)}
   2: {Wednesdays: Array(2)}
   3: {Fridays: Array(2)}
   4: {Wednesdays: Array(2)}
   5: {Fridays: Array(2)}
   6: {Wednesdays: Array(2)}
   7: {Fridays: Array(2)}

[]

As you can see, the tempRemovedTimeRanges reveals an array of objects representing days.

Allow me to expand the first object 0: {Wednesdays: Array(2)} further.
Kindly note that all objects share a similar structure as the first object 0: {Wednesdays: Array(2)}

(8) [{…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}]
  0: 
   Wednesdays: Array(2)
      0: {T_04:00_Start: 1703034000, T_08:00_End: 1703048400}
      1: {T_04:00_Start: 1703638800, T_08:00_End: 1703653200}
  1: {Fridays: Array(2)}
  2: {Wednesdays: Array(2)}
  3: {Fridays: Array(2)}
  4: {Wednesdays: Array(2)}
  5: {Fridays: Array(2)}
  6: {Wednesdays: Array(2)}
  7: {Fridays: Array(2)}

The following section represents two time ranges for the Wednesdays object.
The first one is T_04:00_Start to T_08:00_End and T_04:00_Start to T_08:00_End

{T_04:00_Start: 1703034000, T_08:00_End: 1703048400}
{T_04:00_Start: 1703638800, T_08:00_End: 1703653200}

The keys T_04:00_Start, T_08:00_End, T_04:00_Start and T_08:00_End and NOT the values (timestamps) are what I am interesting in capturing for each day in the tempRemovedTimeRanges array

Now going back to my code:

console.log(tempRemovedTimeRanges);

const removedKeys = tempRemovedTimeRanges
  .flatMap(obj => Object.values(obj))
  .filter(dayArray => dayArray.some(dayObj => Object.keys(dayObj)[0] === elementToInsert))
  .flatMap(dayArray =>
    dayArray
      .filter(dayObj => Object.keys(dayObj)[0] === elementToInsert)
      .flatMap(dayObj => dayObj[elementToInsert].flatMap(range => Object.keys(range)))
  );

console.log(removedKeys);

The desired output of console.log(removedKeys); are all the time ranges keys for each day found in the tempRemovedTimeRanges. Those would therefore look like this:

[T_04:00_Start, 
T_08:00_End, 
T_04:00_Start, 
T_08:00_End, 
T_12:00_Start, 
T_16:00_End, 
T_12:00_Start, 
T_16:00_End, 
T_20:00_Start, 
T_00:00_End, 
T_20:00_Start, 
T_00:00_End, 
T_16:00_Start, 
T_20:00_End, 
T_16:00_Start, 
T_20:00_End]

How do I modify my code to do this?