SOURCE

const map = function (a, ...args) { return a.map(...args); };
const reduce = function (a, ...args) { return a.reduce(...args); };
const sum = (x, y) => x + y;
const square = x => x * x;

let data = [1, 1, 3, 5, 5];
let mean = reduce(data, sum) / data.length;
console.log('print avage:', mean);

let deviations = map(data, x => x - mean);
console.log('deviations:', deviations);
let stddev = Math.sqrt(reduce(map(deviations, square), sum) / (data.length - 1));
console.log('stddev:', stddev);