JavaScript: Evaluate the binomial coefficient of two integers n and k

JavaScript fundamental (ES6 Syntax): Exercise-260 with Solution

Write a JavaScript program to evaluate the binomial coefficients of two integers n and k.

• Use Number.isNaN() to check if any of the two values is NaN.
• Check if k is less than 0, greater than or equal to n, equal to 1 or n - 1 and return the appropriate result.
• Check if n - k is less than k and switch their values accordingly.
• Loop from 2 through k and calculate the binomial coefficient.
• Use Math.round() to account for rounding errors in the calculation.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
// Define a function 'binomialCoefficient' to calculate the binomial coefficient of two numbers 'n' and 'k'
const binomialCoefficient = (n, k) => {
  // Return NaN if 'n' or 'k' is not a number
  if (Number.isNaN(n) || Number.isNaN(k)) return NaN;
  // Return 0 if 'k' is less than 0 or 'k' is greater than 'n'
  if (k < 0 || k > n) return 0;
  // Return 1 if 'k' is equal to 0 or 'k' is equal to 'n'
  if (k === 0 || k === n) return 1;
  // Return 'n' if 'k' is equal to 1 or 'k' is equal to 'n' - 1
  if (k === 1 || k === n - 1) return n;
  // If 'n - k' is less than 'k', assign 'n - k' to 'k'
  if (n - k < k) k = n - k;
  // Initialize 'res' to 'n'
  let res = n;
  // Loop from 2 to 'k' (inclusive)
  for (let j = 2; j <= k; j++) {
    // Calculate the binomial coefficient
    res *= (n - j + 1) / j;
  }
  // Round the result and return
  return Math.round(res);
};

// Calculate the binomial coefficient of 8 and 2
console.log(binomialCoefficient(8, 2)); // 28

Output:

28

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-260-1 by w3resource (@w3resource) on CodePen.

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