JavaScript: Calculate the falling factorial of a number

Last update on August 19 2022 21:51:52 (UTC/GMT +8 hours)

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:

Flowchart:

$Flowchart: JavaScript Math - calculate the falling factorial of a number$

Live Demo:

See the Pen javascript-math-exercise-48 by w3resource (@w3resource) on CodePen.

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