Javascript data type: BigInt vs Number

Question

I just came across JavaScript's new data type BigInt. What are some of the real-time use cases where we have to use BigInt vs Number?

I also see that it doesn't have cross-browser compatibility at this point.

Answer 1

MDN doc

BigInt is a built-in object that provides a way to represent whole numbers larger than 2^53 - 1, which is the largest number JavaScript can reliably represent with the Number primitive and represented by the Number.MAX_SAFE_INTEGER constant. BigInt can be used for arbitrarily large integers.

Difference:

• BigInt cannot be used with methods in the built-in Math object and cannot be mixed with instances of Number in operations
• Because coercing between Number and BigInt can lead to loss of precision, it is recommended to only use BigInt when values greater than 2^53 are reasonably expected and not to coerce between the two types.

Answer 2

The differences between BigInt and Number:

	Number	BigInt
Safe Range	Number.MAX_SAFE_INTEGER; loses precision outside of this range	Extremely large integers
Math operations	Supports the Math object	Basic arithmetic operations: + * - % **
Decimal vs. Integer support	Integers and decimals, e.g 1.00, 2.56	Only integers, e.g 1n, 2n. 5n / 2 === 2n
Syntax	No special syntax	Append n to the end of a number literal or use new BigInt('100')
Type Conversion	Automatically converts Number to BigInt in operations	Requires explicit conversion to Number for arithmetic involving Number values
JSON	Supported by default	Not serializable by default

Use BigInt when you need to work with extremely large integers or require precise integer arithmetic without any loss of precision.

Answer 3

The Number object uses a 64-bit floating-point format. With 64 bits allocated in memory, you have a sign bit, 11 bits for exponent, and 52 bits for the mantissa. Since you only have 52 bits to represent the mantissa, you can only safely represent integers between -(2^53 - 1) and 2^53 - 1. So what does this mean for Number and how does BigInt address it? Examples are usually helpful:

const nval1 = 9007199254740991 + 1
const nval2 = 9007199254740991 + 2
nval1 === nval2
# => true

Clearly, by using the comparison operator with numbers that extend beyond Number.MAX_SAFE_INTEGER leads to some unexpected results. Now let's try it with BigInt:

const bval1 =  9007199254740991n + 1n
const bval2 =  9007199254740991n + 2n
bval1 === bval2
# => false

In terms of practical use, BigInt was added to ES2020 to allow the representation of 64-bit integers, which are required for compatibility with many other programming languages and APIs.