Calculates the standard deviation of an array of numbers

Standard deviation in JavaScript.js

/**
 * Calculates the standard deviation of an array of numbers.
 *
 * @param {Array} arr - The array of numbers.
 * @param {Boolean} usePopulation - Optional. If true, the function uses the population standard deviation formula. Default is false, which uses the sample standard deviation formula.
 * @return {Number} - The standard deviation of the array.
 */
const standardDeviation = (arr, usePopulation = false) => {
    const n = arr.length
    let sum = 0
    let mean = 0

    for (let i = 0; i < n; i++) {
        sum += arr[i]
    }

    mean = sum / n

    let sumOfSqDiff = 0

    for (let i = 0; i < n; i++) {
        sumOfSqDiff += (arr[i] - mean) ** 2
    }

    return Math.sqrt(sumOfSqDiff / (n - (usePopulation ? 0 : 1)))
}


// sample standard deviation
standardDeviation([10, 2, 38, 23, 38, 23, 21]) // 13.284434142114991

// population standard deviation
standardDeviation([10, 2, 38, 23, 38, 23, 21], true) // 12.29899614287479;