["first", "second", "third"]
{answer1: "first", answer2: "second", answer3: "third"} и так сколько этих самих элементов в массиве.
const obj = Object.fromEntries(arr.map((n, i) => [ `answer${i + 1}`, n ]));
const obj = arr.reduce((acc, n, i) => (acc['answer' + ++i] = n, acc), {});
const obj = {};
for (let i = 0; i < arr.length; i++) {
obj['answer'.concat(-~i)] = arr[i];
}