BigInt primitives are a relatively new addition to
JavaScript, allowing mathematical operations on numbers outside the range
allowed by Number. To create a BigInt, append n to the end of a number
literal, or pass an integer or numeric string value to the BigInt() function.
const myNumber = 9999999999999999;
const myBigInt = 9999999999999999n;
typeof myNumber;
> "number"
typeof myBigInt;
> "bigint"
myNumber;
> 10000000000000000
myBigInt;
> 9999999999999999n
In this example, 9999999999999999 is outside the range of digits that can be
safely represented by Number, causing a rounding error.
BigInt values don't inherit the methods and properties by the Number object
provides, and they can't be used with the methods JavaScript's built-in Math
object provides. Most importantly, you can't mix BigInt and Number primitives in
standard arithmetic operations:
9999999999999999n + 5
> Uncaught TypeError: can't convert BigInt to number
To do arithmetic with BigInts, you must define both operands as BigInt values:
console.log( 9999999999999999 + 10 ); // Off by one
> 10000000000000010
console.log( 9999999999999999n + 10n );
> 10000000000000009n