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Javascript factorial

Ticha Godwill Nji on April 21, 2024

Hey everyone! I've stumbled upon this interesting JavaScript code that calculates the factorial of a number, and I'd love to hear your thoughts on...
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sakko profile image
SaKKo • 
const factorialMemo = {}
function factorial(n) {
  if (n === 0 || n === 1) {
    return 1;
  }
  if (!factorialMemo[n]) {
    factorialMemo[n] = n * factorial(n - 1)
  }
  return factorialMemo[n];
}
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For me, I would prefer to memoize the result. I'm not too worried about coding styles. As long as it is easy to read and it's correctly computed.

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ticha profile image
Ticha Godwill Nji •

There are many coding styles and it is worth noting that one size doesn't fit all. So, it is totally ok to have your own coding style as long as the code follows the code practices and industry standards.

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SaKKo •

My point is just to improve performance.

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Ticha Godwill Nji •

I get it

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efpage profile image
Eckehard • • Edited

You can use a simple loop, but recursion can be shorter:

   // Loop
    function fac1(n) {
      let k = 1
      for (let i = 1; i <= n; i++)
        k = k * i
      return k
    }
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With respect to your code: Why not check for (n <= 1) ? And this is a perfect case for the ternary operator, so your code could look like this:

    function factorial(n) {
       return (n <= 1) ?  1 : n * factorial(n - 1);
    }
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Ticha Godwill Nji •

Smart thinking.

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Eckehard •

Thank you much!

Talking about improvements: else after return is superfluous. So, your unchanged code should look like this:

function factorial(n) {
    if (n === 0 || n === 1) 
        return 1;
    return n * factorial(n - 1);
}
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And your code is a bit dangerouse: see what happens, if you try factorial(-1). Checking for <=1 covers this too....

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Ticha Godwill Nji •

Thank you for pointing this out to me. It should cover negative numbers

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Jon Randy 🎖️ • • Edited

😝

// Loop
const fac = (n, k=1) => {for (;n--;k*=n+1){} return k}
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Ticha Godwill Nji •

Smart thinking @jonrandy

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Amin •