To compute the sum and average of elements in an array with JavaScript, we use the reduce method.
For instance, we write
const average = (arr) => arr.reduce((p, c) => p + c, 0) / arr.length;
const result = average([4, 4, 5, 6, 6]);
console.log(result);
to define the average function that calls arr.reduce to return the sum of the entries in arr.
And we divide the sum by arr.length array length to get the average.
Then we call average to return the average of the entries in [4, 4, 5, 6, 6].
