mirror of
https://github.com/TheAlgorithms/JavaScript.git
synced 2025-07-05 08:16:50 +08:00
35 lines
1.3 KiB
JavaScript
35 lines
1.3 KiB
JavaScript
/*
|
|
Returns the sum of a geometric progression
|
|
Article on Geometric Progression: https://en.wikipedia.org/wiki/Geometric_series
|
|
Examples:
|
|
> sumOfGeometricProgression(2, 0.5, 6)
|
|
3.9375
|
|
> sumOfGeometricProgression(0.5, 10, 3)
|
|
55.5
|
|
> sumOfGeometricProgression(0.5, 10, Infinity)
|
|
Error: The geometric progression is diverging, and its sum cannot be calculated
|
|
*/
|
|
|
|
/**
|
|
*
|
|
* @param {Number} firstTerm The first term of the geometric progression
|
|
* @param {Number} commonRatio The common ratio of the geometric progression
|
|
* @param {Number} numOfTerms The number of terms in the progression
|
|
*/
|
|
function sumOfGeometricProgression (firstTerm, commonRatio, numOfTerms) {
|
|
if (!Number.isFinite(numOfTerms)) {
|
|
/*
|
|
If the number of Terms is Infinity, the common ratio needs to be less than 1 to be a convergent geometric progression
|
|
Article on Convergent Series: https://en.wikipedia.org/wiki/Convergent_series
|
|
*/
|
|
if (Math.abs(commonRatio) < 1) return firstTerm / (1 - commonRatio)
|
|
throw new Error('The geometric progression is diverging, and its sum cannot be calculated')
|
|
}
|
|
|
|
if (commonRatio === 1) return firstTerm * numOfTerms
|
|
|
|
return (firstTerm * (Math.pow(commonRatio, numOfTerms) - 1)) / (commonRatio - 1)
|
|
}
|
|
|
|
export { sumOfGeometricProgression }
|