How can I put an object inside an array with different properties

So I'm trying to make an array with different properties for each day of the week.

I have this array:

const [fullData, setFullData] = useState([{index:-1,exercise:""}])

So when user clicks on Monday for instance, I have a bunch of exercises for him to choose. For each exercise I want to put the index of the weekday( I already have this in my code) lets say 1 and the exercises that he chose.

It would end up with something like:

[{index:1,exercise:"exercise1"},{index:1,exercise:"exercise2"}]

I'm not really sure how to do this cause I have the exercises already in an array:

const [exerciseValues, setExerciseValues] = useState([]);

And my weekday is just a regular variable

  let selectedWeekday_Index:number;

I tried a bunch of examples listed in stackoverflow already but I could implement it to my code, can anybody help me out? My last try ended up with this code - that does not work. If anyone needs more details to understand just ask me and I will update the question with it.

 const acceptExercises = () => {    let selectedElements = [...exerciseValues]    let savedData = [...fullData]    selectedElements.forEach(element => {      let copyData=savedData.map(item=>({        [item.exercise]:element,        [item.index]:selectedWeekday_Index      }))      setFullData(copyData)    });   }