Extra long factorial challenge giving me different result in JavaScript

Question

I think that this code works but in the challenge they asking me to return "15511210043330985984000000" instead of "1.5511210043330984e+25" I don't understand what could be the problem. I've tried putting "BigInt" before my result but that gives me something like "15511210043330985984000000n" this "n" at the end of every number.

function extraLongFactorials(n) {
  let result = 1;
  for(let i = n; i >= 1; i--) {
    result *= i;
  }
  return result;
}

console.log(extraLongFactorials(25));

// should be 15511210043330985984000000

Does this answer your question? [How to avoid scientific notation for large numbers in JavaScript?](https://stackoverflow.com/questions/1685680/how-to-avoid-scientific-notation-for-large-numbers-in-javascript) — Randy Casburn, Mar 31 '21 at 22:08
At some point you will have to reconcile that 1) The only way to produce the output without either scientific notation or the `n` on the BigInt is to us BigInt (your intuition is correct) but you have to call `.toString()` on the BigInt to get the output you desire; 2) JavaScript truncates the zeros at the end of the number. 3) be careful not to inadvertently round the number when creating the BigInt. — Randy Casburn, Mar 31 '21 at 22:14

score 2 · Answer 1 · answered Apr 01 '21 at 00:26

Well, I found this solution. It is quite close to what @undg was saying but a little different that is the answer I was expecting.

function extraLongFactorials(n) {
  n = BigInt(n)
  let result = BigInt(1);
  
  
  for(let i = n; i >= 1; i--) {
    result *= i;
  }
  return result.toString();
}

console.log(extraLongFactorials(25)); // 15511210043330985984000000

score 1 · Answer 2 · answered Mar 06 '22 at 13:49

Javascript recursive solution

function extraLongFactorials(n) {
  const factorial = (int) => {
    const bigInt = BigInt(int)
    return bigInt === 0n ? 1n : bigInt * factorial(bigInt - 1n)
  }
  console.log(factorial(n).toString())
}
extraLongFactorials(25)

score 0 · Answer 3 · answered Mar 31 '21 at 22:40

0

Use BigInt() followed by toString()

BigInt(Number.MAX_VALUE).toString()
//'179769313486231570814527423731704356798070567525844996598917476803157260780028538760589558632766878171540458953514382464234321326889464182768467546703537516986049910576551282076245490090389328944075868508455133942304583236903222948165808559332123348274797826204144723168738177180919299881250404026184124858368'

answered Mar 31 '21 at 22:40

undg

787
4
14

I used "BigInt() followed by toString()" it works but that did not give me the answer I expected "15511210043330983907819520" – Erick Apr 01 '21 at 00:17

score 0 · Answer 4 · answered Jun 21 '22 at 19:43

0

an easy solution for this challenge:

function extraLongFactorials(n) {
  let factorial = BigInt(1);
  for (let i = BigInt(2); i <= n; i++) {
    factorial *= i;
  }
  return factorial.toString();
}

answered Jun 21 '22 at 19:43

Masoumeh

1

score 0 · Answer 5 · answered Oct 06 '22 at 18:03

an easy and clean solution is:

 let memoization = [BigInt(0), BigInt(1)];

    const factorial = num => (typeof memoization[num] !== 'number')
        ? ((num - BigInt(1)) > 0
            ? (num * factorial(num - BigInt(1)))
            : BigInt(1)
        )
        : memoization[num]

    console.log(String(factorial(BigInt(n))));

score -1 · Answer 6 · edited Jan 17 '23 at 18:48

-1

let extraLongFactorials = (n) => {

    let mult = 1

    while (n >= 1) {

        mult = BigInt(mult) * BigInt(n)

        --n
    }

    console.log(BigInt(mult).toString())
}

edited Jan 17 '23 at 18:48

Asplund

2,254
1
8
19

answered Jan 15 '23 at 17:07

Abhay Kumar Singh

1
1

why are you using `let` to declare a function, are you planning on mutating it later? Also, perhaps it should return the result instad of console logging it. As it stands this function requires modifications to use. I recommend using snippets to showcase functions and console logging the result of the function. Additionally, you are not explaining how this works, please add additional information explaining your solution. – Asplund Jan 17 '23 at 14:41

Extra long factorial challenge giving me different result in JavaScript

6 Answers6