Calculation mistake (javascript)

Question

Was using JavaScript to generator sequence of numbers defined by a specific function.

Link to code (you may need a check at this)

The code actually shows if the terms of the mentioned sequence belongs to another sequence defined by 49n-49. It shows TRUE if it does, and FALSE if it doesn't belong. In fact, I have mathematically proven that it should return TRUE for all the terms. You can try to run it in HTML and all will go well until the 18th term when it does a calculation mistake. At this point I tried to play with the code a little bit and briefed up the problem. Found that actually it was the output that just won't be the correct one. Following is a code that shows the problem:

var a = 18014398509481858
document.write(a - 1)

Now the output to the above script comes out to be 18014398509481856 instead of 18014398509481857. You see there is a difference of 1. Please help.

You may want to use the `BigInt` library; see e.g. [this other thread](https://stackoverflow.com/q/60803903) — ErikMD, Mar 27 '20 at 18:06

score 3 · Accepted Answer · answered Mar 27 '20 at 18:06

Above Number.MAX_SAFE_INTEGER (which is 9007199254740991 in my browser), math stops working correctly. However, javascript has support for a class called BigInt, which lets you use arbitrarily large integers with accurate operations. You just have to construct it with BigInt("18014398509481858") or use the literal 18014398509481858n. Since it's a relatively new feature, if you want to cater to older browsers, you can use a library like BigInteger.

Calculation mistake (javascript)

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