JavaScript BigInt

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JavaScript BigInt


JavaScript BigInt variables are used to store big integer values
that are too big to be represented by a normal JavaScript Number.

JavaScript Integer Accuracy
JavaScript integers are only accurate up to 15 digits:

Integer Precision

let x = 999999999999999;
let y = 9999999999999999;

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In JavaScript, all numbers are stored in a 64-bit floating-point format (IEEE 754 standard).
With this standard, large integer cannot be exactly represented and will be rounded.
Because of this, JavaScript can only safely represent integers:
Up to 9007199254740991 +(253-1)
and
Down to -9007199254740991 -(253-1).
Integer values outside this range lose precision.

How to Create a BigInt
To create a BigInt, append n to the end of an integer or call
BigInt():

Examples

let x = 9999999999999999;
let y = 9999999999999999n;

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let x = 1234567890123456789012345n;
let y = BigInt(1234567890123456789012345)

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BigInt: A new JavaScript Datatype
The JavaScript typeof a BigInt is "bigint":

Example

let x = BigInt(999999999999999);
let type = typeof x;

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BigInt is the second numeric data type in JavaScript
(after Number).
With BigInt the total number of supported data types in JavaScript is 8:

1. String
2. Number
3. Bigint
4. Boolean
5. Undefined
6. Null
7. Symbol
8. Object


BigInt Operators
Operators that can be used on a JavaScript Number
can also be used on a BigInt.

BigInt Multiplication Example

let x = 9007199254740995n;
let y = 9007199254740995n;
let z = x * y;

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Notes
Arithmetic between a BigInt
and a Number is not allowed (type conversion lose information).
Unsigned right shift (>>>) can not be done on a BigInt
(it does not have a fixed width).


BigInt Decimals
A BigInt can not have decimals.

BigInt Division Example

let x = 5n;
let y = x / 2;
// Error: Cannot mix BigInt and other types, use explicit conversion.


let x = 5n;
let y = Number(x) / 2;

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BigInt Hex, Octal and Binary
BigInt can also be written in hexadecimal, octal, or binary notation:

BigInt Hex Example

let hex = 0x20000000000003n;
let oct = 0o400000000000000003n;
let bin = 0b100000000000000000000000000000000000000000000000000011n;

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Precision Curiosity
Rounding can compromise program security:

MAX_SAFE_INTEGER Example

9007199254740992 === 9007199254740993; // is true !!!

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Browser Support
BigInt is supported in all browsers since September 2020:










Chrome 67
Edge 79
Firefox 68
Safari 14
Opera 54


May 2018
Jan 2020
Jul 2019
Sep 2020
Jun 2018










Minimum and Maximum Safe Integers
ES6 added max and min properties to the Number object:

MAX_SAFE_INTEGER
MIN_SAFE_INTEGER


MAX_SAFE_INTEGER Example

let x = Number.MAX_SAFE_INTEGER;

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MIN_SAFE_INTEGER Example

let x = Number.MIN_SAFE_INTEGER;

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New Number Methods
ES6 also added 2 new methods to the Number object:

Number.isInteger()
Number.isSafeInteger()


The Number.isInteger() Method
The Number.isInteger() method returns true if the argument is an integer.

Example: isInteger()

Number.isInteger(10);
Number.isInteger(10.5);

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The Number.isSafeInteger() Method
A safe integer is an integer that can be exactly represented as a double precision number.
The Number.isSafeInteger() method returns true if the argument is a safe integer.

Example isSafeInteger()

Number.isSafeInteger(10);
Number.isSafeInteger(12345678901234567890);

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Safe integers are all integers from -(253 - 1) to +(253 - 1).
This is safe: 9007199254740991. This is not safe: 9007199254740992.













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Reference: https://www.w3schools.com/js/js_bigint.asp