Simple stats API example

stats-api.js

var statsApi = (function () {
    'use strict';

    var square = pow(2);
    var squareRoot = pow(0.5);
    
    function getStandardDeviation (values) {
        var xBar = getMean(values);
        var computedValues = values.map(subtractMeanAndSquare(xBar));
        return squareRoot(getMean(computedValues));
    }
    
    function getMean (values) {
        return sum(values) / values.length;
    }
    
    function subtractMeanAndSquare (mean) {
        return function (value) {
            return square(value - mean);
        };
    }
    
    function pow(power) {
        return function (value) {
            return Math.pow(value, power);
        }
    }
    
    function sum (values) {
        return values.reduce(add, 0);
    }
    
    function add (a, b) {
        return a + b;
    }
    
    return {
        getMean: getMean,
        getStandardDeviation: getStandardDeviation
    };
    
})();