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 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

To see the library in action see radix

If an even smaller and simpler library is required see big.js.
It's half the size with half the methods and only works with decimal numbers; 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 bignumber.min.js, which is bignumber.js minified using uglify-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.
It can then be loaded with require('bignumber.js').

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, String or 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 and the rounding mode for 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/issues/comments to:

Michael Mclaughlin
M8ch88l@gmail.com

Bitcoin donations to:
1GMiXasawxpBxj5ggcNRP8zyAsJmoyeWQi
Thank you!

Licence

See LICENCE.

Change Log

####1.0.0

• 8/11/2012 Initial release