how to calculate average of array in javascript

1const arrAvg = arr => arr.reduce((a,b) => a + b, 0) / arr.length

1const average = (...args) => args.reduce((a, b) => a + b) / args.length;
2
3// Example
4average(1, 2, 3, 4);    // 2.5

1var total = 0;
2for(var i = 0; i < grades.length; i++) {
3    total += grades[i];
4}
5var avg = total / grades.length;
6

1var a = [80, 77, 88, 95, 68];
2
3console.log(eval(a.join('+'))/a.length)