Example of matrix manipulate with ES6

average-sum.js

/*
 * Function that calculate the average of a number
 *
 * @param {Number} num 
 * @param {Number} divisor
 * @return {Number} simple arithmetic average of num
 *
 */

var calcAverage = (num, divisor) => (num / divisor).toFixed(2);

es6-matrix.js

var grades = [[90, 85, 78],[85, 95, 94],[92, 83, 87]];

grades.forEach((row, i) => {
  let total = row.reduce((total, num) => total += num);
  let average = calcAverage(total, row.length);
  
  console.log('Student ${i + 1} average: ${average}');
});