What is jsbi?
JSBI is a pureJavaScript implementation of the official ECMAScript BigInt proposal, which 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. JSBI is useful for performing arbitraryprecision arithmetic in JavaScript.
What are jsbi's main functionalities?
Arithmetic Operations
JSBI allows performing basic arithmetic operations such as addition, subtraction, multiplication, division, and finding the remainder between large integers.
const JSBI = require('jsbi');
const bigInt1 = JSBI.BigInt('123456789012345678901234567890');
const bigInt2 = JSBI.BigInt('987654321098765432109876543210');
const sum = JSBI.add(bigInt1, bigInt2);
const difference = JSBI.subtract(bigInt2, bigInt1);
const product = JSBI.multiply(bigInt1, bigInt2);
const quotient = JSBI.divide(bigInt2, bigInt1);
const remainder = JSBI.remainder(bigInt2, bigInt1);
Comparison Operations
JSBI can compare BigInt numbers to check for equality, or to see if one is greater than or less than another.
const JSBI = require('jsbi');
const bigInt1 = JSBI.BigInt('1234567890');
const bigInt2 = JSBI.BigInt('1234567890');
const bigInt3 = JSBI.BigInt('9876543210');
const isEqual = JSBI.equal(bigInt1, bigInt2); // true
const isLessThan = JSBI.lessThan(bigInt1, bigInt3); // true
const isGreaterThan = JSBI.greaterThan(bigInt3, bigInt1); // true
Bitwise Operations
JSBI supports bitwise operations such as AND, OR, and XOR, which are useful for manipulating large integers at the bit level.
const JSBI = require('jsbi');
const bigInt1 = JSBI.BigInt('1234567890');
const bigInt2 = JSBI.BigInt('9876543210');
const bitwiseAnd = JSBI.bitwiseAnd(bigInt1, bigInt2);
const bitwiseOr = JSBI.bitwiseOr(bigInt1, bigInt2);
const bitwiseXor = JSBI.bitwiseXor(bigInt1, bigInt2);
Other packages similar to jsbi
biginteger
biginteger is another arbitraryprecision integer arithmetic library for JavaScript. It offers similar functionalities to JSBI but also includes additional features like primality testing, which JSBI does not support.
bignumber.js
bignumber.js is a wellknown library for working with large floatingpoint numbers as well as integers. It provides more features than JSBI, including support for decimal arithmetic and more advanced mathematical functions.
JSBI — pureJavaScript BigInts
JSBI is a pureJavaScript implementation of the ECMAScript BigInt proposal, which officially became a part of the JavaScript language in ES2020.
Installation
npm install jsbi save
Usage
import JSBI from './jsbi.mjs';
const max = JSBI.BigInt(Number.MAX_SAFE_INTEGER);
console.log(String(max));
const other = JSBI.BigInt('2');
const result = JSBI.add(max, other);
console.log(String(result));
Note: explicitly call toString
on any JSBI
instances when console.log()
ing them to see their numeric representation (e.g. String(max)
or max.toString()
). Without it (e.g. console.log(max)
), you’ll instead see the object that represents the value.
Use babelplugintransformjsbitobigint to transpile JSBI code into native BigInt code.
Refer to the detailed instructions below for more information.
Why?
Native BigInts are already shipping in modern browsers (at the time of this writing, Google Chrome 67+, Opera 54+, Firefox 68+, Edge 79+, Safari 14+) and Node.js (v10.4+), but some users are still running older browsers — which means you can't use them yet if you want your code to run everywhere.
To use BigInts in code that you want to run everywhere, you need a library. But there’s a difficulty: the BigInt proposal changes the behavior of operators (like +
, >=
, etc.) to work on BigInts. These changes are impossible to polyfill directly; and they are also making it infeasible (in most cases) to transpile BigInt code to fallback code using Babel or similar tools. The reason is that such a transpilation would have to replace every single operator in the program with a call to some function that performs type checks on its inputs, which would incur an unacceptable performance penalty.
The solution is to do it the other way round: write code using a library’s syntax, and transpile it to native BigInt code when available. JSBI is designed for exactly this purpose: it provides a BigInt “polyfill” implementation that behaves exactly like the upcoming native BigInts, but with a syntax that you can ship on all browsers, today.
Its advantages over other, existing biginteger libraries are:
 it behaves exactly like native BigInts do where they are available, so to eventually migrate to those, you can mechanically update your code’s syntax; no rethinking of its logic will be required.
 strong focus on performance. On average, JSBI is performancecompetitive with the native implementation that Google Chrome is currently shipping. (Note: we expect this statement to gradually become outdated as browsers invest in additional optimizations.)
How?
Except for mechanical differences in syntax, you use JSBIBigInts just like you would use native BigInts. Some things even look the same, after you replace BigInt
with JSBI.BigInt
:
Operation  native BigInts  JSBI 

Creation from String  a = BigInt('456')  a = JSBI.BigInt('456') 
Creation from Number  a = BigInt(789)  a = JSBI.BigInt(789) 
Conversion to String  a.toString(radix)  a.toString(radix) 
Conversion to Number  Number(a)  JSBI.toNumber(a) 
Truncation  BigInt.asIntN(64, a)  JSBI.asIntN(64, a) 
 BigInt.asUintN(64, a)  JSBI.asUintN(64, a) 
Type check  typeof a === 'bigint'  a instanceof JSBI 
Most operators are replaced by static functions:
Operation  native BigInts  JSBI 

Addition  c = a + b  c = JSBI.add(a, b) 
Subtraction  c = a  b  c = JSBI.subtract(a, b) 
Multiplication  c = a * b  c = JSBI.multiply(a, b) 
Division  c = a / b  c = JSBI.divide(a, b) 
Remainder  c = a % b  c = JSBI.remainder(a, b) 
Exponentiation  c = a ** b  c = JSBI.exponentiate(a, b) 
Negation  b = a  b = JSBI.unaryMinus(a) 
Bitwise negation  b = ~a  b = JSBI.bitwiseNot(a) 
Left shifting  c = a << b  c = JSBI.leftShift(a, b) 
Right shifting  c = a >> b  c = JSBI.signedRightShift(a, b) 
Bitwise “and”  c = a & b  c = JSBI.bitwiseAnd(a, b) 
Bitwise “or”  c = a  b  c = JSBI.bitwiseOr(a, b) 
Bitwise “xor”  c = a ^ b  c = JSBI.bitwiseXor(a, b) 
Comparison to other BigInts  a === b  JSBI.equal(a, b) 
 a !== b  JSBI.notEqual(a, b) 
 a < b  JSBI.lessThan(a, b) 
 a <= b  JSBI.lessThanOrEqual(a, b) 
 a > b  JSBI.greaterThan(a, b) 
 a >= b  JSBI.greaterThanOrEqual(a, b) 
The functions above operate only on BigInts. (They don’t perform type checks in the current implementation, because such checks are a waste of time when we assume that you know what you’re doing. Don’t try to call them with other inputs, or you’ll get “interesting” failures!)
Some operations are particularly interesting when you give them inputs of mixed types, e.g. comparing a BigInt to a Number, or concatenating a string with a BigInt. They are implemented as static functions named after the respective native operators:
Operation  native BigInts  JSBI 

Abstract equality comparison  x == y  JSBI.EQ(x, y) 
Generic “not equal”  x != y  JSBI.NE(x, y) 
Generic “less than”  x < y  JSBI.LT(x, y) 
Generic “less than or equal”  x <= y  JSBI.LE(x, y) 
Generic “greater than”  x > y  JSBI.GT(x, y) 
Generic “greater than or equal”  x >= y  JSBI.GE(x, y) 
Generic addition  x + y  JSBI.ADD(x, y) 
The variable names x
and y
here indicate that the variables can refer to anything, for example: JSBI.GT(101.5, BigInt('100'))
or str = JSBI.ADD('result: ', BigInt('0x2A'))
.
Unfortunately, there are also a few things that are not supported at all:
Unsupported operation  native BigInts  JSBI 

literals  a = 123n;  N/A ☹ 
increment  a++  N/A ☹ 
 a + 1n  JSBI.add(a, JSBI.BigInt('1')) 
decrement  a  N/A ☹ 
 a  1n  JSBI.subtract(a, JSBI.BigInt('1')) 
It is impossible to replicate the exact behavior of the native ++
and 
operators in a polyfill/library. Since JSBI is intended to be transpiled away eventually, it doesn’t provide a similarbutdifferent alternative. You can use JSBI.add()
and JSBI.subtract()
instead.
Since version 4.2.0, polyfills for DataView
operations are included (where dv
is a DataView
, i
is an index, le
is an optional boolean indicating little endian mode, and x
is a BigInt
or a JSBI
instance, respectively):
native BigInts/DataViews  JSBI 

dv.getBigInt64(i, le)  JSBI.DataViewGetBigInt64(dv, i, le) 
dv.setBigInt64(i, x, le)  JSBI.DataViewSetBigInt64(dv, i, x, le) 
dv.getBigUint64(i, le)  JSBI.DataViewGetBigUint64(dv, i, le) 
dv.setBigUint64(i, x, le)  JSBI.DataViewSetBigUint64(dv, i, x, le) 
When?
Now! The JSBI library is ready for use today.
Once BigInts are natively supported everywhere, use babelplugintransformjsbitobigint to transpile your JSBI code into native BigInt code once and for all.
View our issue tracker to learn more about out our future plans for JSBI, and please join the discussion!
A more vague future plan is to use the JSBI library (or an extension to it) as a staging ground for additional BigIntrelated functionality. The official proposal is intentionally somewhat minimal, and leaves further “library functions” for followup proposals. Examples are a combined exp
+mod
function, and bit manipulation functions.
Development

Clone this repository and cd
into the local directory.

Use the Node.js version specified in .nvmrc
:
nvm use

Install development dependencies:
npm install

Run the tests:
npm test
See npm run
for the list of commands.
For maintainers
How to publish a new release

On the main
branch, bump the version number in package.json
:
npm version patch m 'Release v%s'
Instead of patch
, use minor
or major
as needed.
Note that this produces a Git commit + tag.

Push the release commit and tag:
git push && git push tags
Our CI then automatically publishes the new release to npm.