Comparing the performance of recursive and looped factorial function in JavaScript


We will be writing two JavaScript functions, the job of both the functions will be to take in a number and return its factorial.

The first function should make use of a for loop or while loop to compute the factorial. Whereas the second function should compute the factorial using a recursive approach.

Lastly, we should compare the times taken by these functions over a large number of iterations.

Example

Following is the code −

const factorial = (num = 1) => {
   let result = 1;
   for (let i = 2; i <= num; i += 1) {
      result *= i;
   }
   return result;
}
const factorialRecursive = (num = 1) => {
   if(num > 1){
      return num * factorialRecursive(num - 1);
   }else{
      return 1;
   }
};
const ITERATIONS = 100000000;
const num = 12;
console.time('Looping Approach');
for(let i = 0; i < ITERATIONS; i++){
   factorial(num);
};
console.timeEnd('Looping Approach');
console.time('Recursive Approach');
for(let j = 0; j < ITERATIONS; j++){
   factorialRecursive(num);
};
console.timeEnd('Recursive Approach');

Output

Following is the output on console −

Looping Approach: 886.720ms
Recursive Approach: 6526.203ms

This time taken will vary from machine to machine by the ratio is bound to remain more or less the same.

Updated on: 10-Dec-2020

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