bignumber.js

What is bignumber.js?

The bignumber.js package is a JavaScript library for arbitrary-precision decimal and non-decimal arithmetic. It allows for high-precision calculations that are necessary when dealing with very large or very small numbers that cannot be accurately represented with JavaScript's native Number type.

What are bignumber.js's main functionalities?

Arithmetic Operations

Perform precise arithmetic operations such as addition, subtraction, multiplication, and division.

"use strict"; const BigNumber = require('bignumber.js'); let x = new BigNumber(123.4567); let y = new BigNumber('123456.7e-3'); let z = x.plus(y); console.log(z.toString()); // '246.9134'

Chaining Methods

Allows for method chaining to perform multiple operations sequentially on a BigNumber instance.

"use strict"; const BigNumber = require('bignumber.js'); let result = new BigNumber('111.1111111').plus('0.0000001').times('3').sqrt().toPrecision(10); console.log(result); // '1.732050808'

Comparison

Compare two BigNumber instances to determine the relational state.

"use strict"; const BigNumber = require('bignumber.js'); let a = new BigNumber('2'); let b = new BigNumber('3'); console.log(a.isLessThan(b)); // true

Rounding

Round a BigNumber to a specified number of decimal places.

"use strict"; const BigNumber = require('bignumber.js'); let number = new BigNumber('123.4567'); let rounded = number.toFixed(2); console.log(rounded); // '123.46'

Conversion

Convert a BigNumber to a different base or to a string representation.

"use strict"; const BigNumber = require('bignumber.js'); let number = new BigNumber('123456.789e-3'); let inBase10 = number.toString(10); console.log(inBase10); // '123.456789'

Other packages similar to bignumber.js

decimal.js

Similar to bignumber.js, decimal.js is a library for arbitrary-precision Decimal arithmetic. It provides a similar API but focuses strictly on decimal numbers, whereas bignumber.js can handle non-decimal (base 2-36) numbers as well.

big.js

big.js is another arbitrary-precision arithmetic library. It is smaller and simpler than bignumber.js, but it does not include some of the more advanced features and functions that bignumber.js provides.

mathjs

mathjs is an extensive math library for JavaScript and Node.js, which includes functionality for arbitrary-precision arithmetic. It offers a wider range of mathematical functions and data types compared to bignumber.js, but it is also larger in size.

README

bignumber.js

A JavaScript library for arbitrary-precision decimal and non-decimal arithmetic.

Features

• Faster, smaller, and perhaps easier to use than JavaScript versions of Java's BigDecimal
• 5 KB minified and gzipped
• Simple API but full-featured
• Works with numbers with or without fraction digits in bases from 2 to 36 inclusive
• Replicates the toExponential, toFixed, toPrecision and toString methods of JavaScript's Number type
• Includes a toFraction and a squareRoot method
• Stores values in an accessible decimal floating point format
• No dependencies
• Comprehensive documentation and test set

If an even smaller and simpler library is required see big.js.
It's half the size but only works with decimal numbers and only has half the methods.
It also does not allow NaN or Infinity, or have the configuration options of this library.

Load

The library is the single JavaScript file bignumber.js (or minified, bignumber.min.js).

It can be loaded via a script tag in an HTML document for the browser

<script src='./relative/path/to/bignumber.js'></script>

or as a CommonJS, Node.js or AMD module using require.

For Node, put the bignumber.js file into the same directory as the file that is requiring it and use

var BigNumber = require('./bignumber'); 

or put it in a node_modules directory within the directory and use require('bignumber').

The library is also available from the npm registry, so

$ npm install bignumber.js

will install this entire directory in a node_modules directory within the current directory.

To load with AMD loader libraries such as requireJS:

require(['bignumber'], function(BigNumber) {  
    // Use BigNumber here in local scope. No global BigNumber. 
});

Use

In all examples below, var, semicolons and toString calls are not shown.
If a commented-out value is in quotes it means toString has been called on the preceding expression.

The library exports a single function: BigNumber, the constructor of BigNumber instances.
It accepts a value of type Number (up to 15 significant digits only), String or BigNumber Object,

x = new BigNumber(123.4567)
y = BigNumber('123456.7e-3')                     // 'new' is optional
z = new BigNumber(x)
x.equals(y) && y.equals(z) && x.equals(z)        // true

and a base from 2 to 36 inclusive can be specified.

x = new BigNumber(1011, 2)           // "11" 
y = new BigNumber('zz.9', 36)        // "1295.25"
z = x.plus(y)                        // "1306.25"

A BigNumber is immutable in the sense that it is not changed by its methods.

0.3 - 0.1                     // 0.19999999999999998  
x = new BigNumber(0.3)            
x.minus(0.1)                  // "0.2"
x                             // "0.3"

The methods that return a BigNumber can be chained.

x.dividedBy(y).plus(z).times(9).floor()
x.times('1.23456780123456789e+9').plus(9876.5432321).dividedBy('4444562598.111772').ceil()

Method names over 5 letters in length have a shorter alias.

x.squareRoot().dividedBy(y).toPower(3).equals(x.sqrt().div(y).pow(3))         // true
x.cmp(y.mod(z).neg()) == 1 && x.comparedTo(y.modulo(z).negated()) == 1        // true

Like JavaScript's Number type, there are toExponential, toFixed and toPrecision methods

x = new BigNumber(255.5)        
x.toExponential(5)              // "2.55500e+2"
x.toFixed(5)                    // "255.50000"
x.toPrecision(5)                // "255.50"

and a base can be specified for toString.

x.toString(16)        // "ff.8"

The maximum number of decimal places of, and the rounding mode applied to, the results of operations involving division (i.e. division, square root, base conversion, and negative power operations) is set by a configuration object passed to the config method of the BigNumber constructor.
The other arithmetic operations always give the exact result.

BigNumber.config({ DECIMAL_PLACES: 10, ROUNDING_MODE: 4 })
// Alternatively, BigNumber.config( 10, 4 );

x = new BigNumber(2);
y = new BigNumber(3);        
z = x.div(y)                 // "0.6666666667"
z.sqrt()                     // "0.8164965809"
z.pow(-3)                    // "3.3749999995"
z.toString(2)                // "0.1010101011"
z.times(z)                   // "0.44444444448888888889"
z.times(z).round(10)         // "0.4444444445"

There is a toFraction method with an optional maximum denominator argument

y = new BigNumber(355)
pi = y.dividedBy(113)        // "3.1415929204"
pi.toFraction()              // [ "7853982301", "2500000000" ]
pi.toFraction(1000)          // [ "355", "113" ]

and isNaN and isFinite methods, as NaN and Infinity are valid BigNumber values.

x = new BigNumber(NaN)                                           // "NaN"
y = new BigNumber(Infinity)                                      // "Infinity"
x.isNaN() && !y.isNaN() && !x.isFinite() && !y.isFinite()        // true

The value of a BigNumber is stored in a decimal floating point format in terms of a coefficient, exponent and sign.

x = new BigNumber(-123.456); 
x.c                                 // "1,2,3,4,5,6"    coefficient (i.e. significand)
x.e                                 // 2                exponent 
x.s                                 // -1               sign

For futher information see the API reference in the doc folder.

Test

The test directory contains the test scripts for each method.

The tests can be run with Node or a browser.

For a quick test of all the methods, from a command-line shell at the test/ directory

$ node quick-test

To test a single method in more depth, e.g.

$ node toFraction

To test all the methods in more depth

$ node every-test

For the browser, see quick-test.html, single-test.html and every-test.html in the test/browser directory.

bignumber-vs-number.html enables some of the methods of bignumber.js to be compared with those of JavaScript's Number type.

Performance

The perf directory contains two applications and a lib directory containing the BigDecimal libraries used by both.

bignumber-vs-bigdecimal.html tests the performance of bignumber.js against the JavaScript translations of two versions of BigDecimal, its use should be more or less self-explanatory. (The GWT version doesn't work in IE 6.)

• GWT: java.math.BigDecimal
  https://github.com/iriscouch/bigdecimal.js
• ICU4J: com.ibm.icu.math.BigDecimal
  https://github.com/dtrebbien/BigDecimal.js

The BigDecimal in Node's npm registry is the GWT version. Despite its seeming popularity I have found it to have some serious bugs, see the Node script perf/lib/bigdecimal_GWT/bugs.js for examples of flaws in its remainder, divide and compareTo methods.

bigtime.js is a Node command-line application which tests the performance of bignumber.js against the GWT version of BigDecimal from the npm registry.

For example, to compare the time taken by the bignumber.js plus method and the BigDecimal add method:

$ node bigtime plus 10000 40      

This will time 10000 calls to each, using operands of up to 40 random digits and will check that the results match.

For help:

$ node bigtime -h

See the README in the directory for more information.

Build

I.e. minify.

For Node, if uglify-js is installed globally ( npm install uglify-js -g ) then

uglifyjs -o ./bignumber.min.js ./bignumber.js

will create bignumber.min.js.

Feedback

Bugs: surely not! Open an issue, please.
Other feedback to:

Michael
[e-mail]

Bitcoin donation to:
1KdnpLRSkWJs4FXPzj7pQ39H4Ur6Urydti
Thank you

Licence

MIT.

See LICENCE.

Change Log

####1.1.1

• 22/8/2013 Show original value in constructor error message.

####1.1.0

• 1/8/2013 Allow numbers with trailing radix point.

####1.0.1

• Bugfix: error messages with incorrect method name

####1.0.0

• 8/11/2012 Initial release

Changelog

1.1.1

• 22/8/2013
• Show original value in constructor error message.