JavaScript: Calculate the falling factorial of a number
JavaScript Math: Exercise-48 with Solution
Write a JavaScript function to calculate the falling factorial of a number.
Let x be a real number (but usually an integer).
Let k be a positive integer.
Then x to the (power of) k falling is:
This is called the kth falling factorial power of x.
Sample Solution:-
HTML Code:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>JavaScript function to calculate the falling factorial of a number</title>
</head>
<body>
</body>
</html>
JavaScript Code:
function fallingFactorial(n, k)
{
var i = (n - k + 1),
r = 1;
if (n < 0)
{
throw new Error("n must be positive.");
}
if (k > n)
{
throw new Error("k cannot be greater than n.");
}
while (i <= n)
{
r *= i++;
}
return r;
}
console.log(fallingFactorial(10, 2));
Sample Output:
90
Flowchart:

Live Demo:
See the Pen javascript-math-exercise-48 by w3resource (@w3resource) on CodePen.
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Previous: Write a JavaScript function to calculate the extended Euclid Algorithm or extended GCD.
Next: Write a JavaScript function to calculate Lanczos approximation gamma.
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