Finding the average of an array using JS [duplicate]

Answer 1

For the second part of your question you can use reduce to good effect here:

const grades = [80, 77, 88, 95, 68];

function getAvg(grades) {
  const total = grades.reduce((acc, c) => acc + c, 0);
  return total / grades.length;
}

const average = getAvg(grades);
console.log(average);

The other answers have given good insight into why you got 68, so I won't repeat it here.