JavaScript: Get the standard deviation of an array of numbers
JavaScript fundamental (ES6 Syntax): Exercise-225 with Solution
Write a JavaScript program to get the standard deviation of an array of numbers.
- Use Array.prototype.reduce() to calculate the mean, variance and the sum of the variance of the values and determine the standard deviation.
- Omit the second argument, usePopulation, to get the sample standard deviation or set it to true to get the population standard deviation.
Sample Solution:
JavaScript Code:
//#Source https://bit.ly/2neWfJ2
const standardDeviation = (arr, usePopulation = false) => {
const mean = arr.reduce((acc, val) => acc + val, 0) / arr.length;
return Math.sqrt(
arr.reduce((acc, val) => acc.concat((val - mean) ** 2), []).reduce((acc, val) => acc + val, 0) /
(arr.length - (usePopulation ? 0 : 1))
);
};
console.log(standardDeviation([10, 2, 38, 23, 38, 23, 21]));
console.log(standardDeviation([10, 2, 38, 23, 38, 23, 21], true));
Sample Output:
13.284434142114991 12.29899614287479
Flowchart:

Live Demo:
See the Pen javascript-basic-exercise-225-1 by w3resource (@w3resource) on CodePen.
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JavaScript: Tips of the Day
How to check whether a string contains a substring in JavaScript?
ECMAScript 6 introduced String.prototype.includes:
const string = "foo"; const substring = "oo"; console.log(string.includes(substring));
includes doesn't have Internet Explorer support, though. In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found:
var string = "foo"; var substring = "oo"; console.log(string.indexOf(substring) !== -1);
Ref: https://bit.ly/3fFFgZv
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