javascriptnode.jsbigintbignum

Divide 2 Bigints (Find percentage change)

I have 2 numbers:

 const a = 61921447244562694144000n;
 const b = 93068664972055293198336n;

and I'm trying to find a percentage change between them.

So far I tried 3 methods - using just numbers, using BigInts and JSBI.

const percentageChange = ((a - b ) / b) * 100n);

This method is not working because this calculation with BigInts will always give just once digit due the limitations with decimals - BigInt always rounds up the number.

With just numbers I got the answer, but it was incorrect (guess because of the large numbers)

JSBI giving many different errors, but I still can't wrap my head arround it:

 let a = JSBI.subtract(oldValue, newValue);

     
 let b = JSBI.divide(a, oldValue);

jsbi errors such as:

TypeError: _.__digit is not a function

or

Error: Convert JSBI instances to native numbers using `toNumber`.
Solution

  • You can change the order of operations:

    const a = 61921447244562694144000n;
const b = 93068664972055293198336n;

const percentageChange = (a - b ) * 100n / b;

console.log(percentageChange.toString());
console.log(Number(percentageChange));

    You can add even more digits:

    const a = 61921447244562694144000n;
const b = 93068664972055293198336n;

const percentageChange = (a - b ) * 1000n / b;

console.log(Number(percentageChange) / 10);