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4.2.1 JS 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;

Try it yourself

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;

Try it yourself

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

Try it yourself

BigInt: A new JavaScript Datatype

The JavaScript typeof a BigInt is "bigint":

Example

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

Try it yourself

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;

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;

Try it yourself

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;

Try it yourself

Precision Curiosity

Rounding can compromise program security:

MAX_SAFE_INTEGER Example

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

Try it yourself

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;

try it yourself

MIN_SAFE_INTEGER Example

let x = Number.MIN_SAFE_INTEGER;

Try it yourself

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);

Try it yourself

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);

Try it yourself

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

JavaScript Fundamentals course home
Module 4. Data Types

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