big.js

What is big.js?

The big.js npm package is a library for arbitrary-precision decimal arithmetic. It allows you to perform calculations on numbers with a large number of digits without losing precision, which is a common issue with JavaScript's native Number type.

What are big.js's main functionalities?

Arithmetic Operations

Perform precise addition, subtraction, multiplication, and division operations.

{"addition": "new Big('0.1').plus(new Big('0.2')).toString()", "subtraction": "new Big('0.3').minus(new Big('0.1')).toString()", "multiplication": "new Big('0.2').times(new Big('0.3')).toString()", "division": "new Big('0.3').div(new Big('0.2')).toString()"}

Comparison Operations

Compare two Big numbers to determine equality, or whether one is greater than or less than the other.

{"equals": "new Big('1.0').eq(new Big('1.00'))", "greaterThan": "new Big('2').gt(new Big('1.9999'))", "lessThan": "new Big('0.1').lt(new Big('0.2'))"}

Rounding

Round Big numbers to a specified number of decimal places, or convert a Big number to a fixed-point notation string.

{"round": "new Big('0.12345').round(2).toString()", "toFixed": "new Big('0.12345').toFixed(2)"}

Configuration

Configure the number of decimal places for rounding and the rounding mode (e.g., round half up, round down, etc.).

{"setDP": "Big.DP = 10", "setRM": "Big.RM = 1"}

Other packages similar to big.js

bignumber.js

bignumber.js is another arbitrary-precision decimal and non-decimal arithmetic library with similar functionality to big.js. It provides more features, such as support for non-decimal bases, but it might be slower for some operations due to its broader scope.

decimal.js

decimal.js is a library for arbitrary-precision arithmetic that is similar to big.js but with additional features like trigonometric and logarithmic functions, which big.js does not have. It also allows for immutable Decimal instances.

fraction.js

fraction.js is focused on rational numbers (fractions) and provides arithmetic operations for them. It is different from big.js, which deals with decimal numbers, but it can be used for high-precision calculations where representing numbers as fractions is more appropriate.

README

big.js

A small, fast JavaScript library for arbitrary-precision decimal arithmetic.

The little sister to bignumber.js. See also decimal.js, and here for the difference between them.

Features

• Faster, smaller and easier-to-use than JavaScript versions of Java's BigDecimal
• Only 5.9 KB minified and 2.7 KB gzipped
• Simple API
• Replicates the toExponential, toFixed and toPrecision methods of JavaScript's Number type
• Includes a sqrt method
• Stores values in an accessible decimal floating point format
• No dependencies
• Comprehensive documentation and test set

Load

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

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

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

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

var Big = require('big.js');

For Node.js, the library is available from the npm registry:

$ npm install big.js

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: Big, the constructor of Big number instances. It accepts a value of type Number, String or Big number Object.

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

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

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

The methods that return a Big number can be chained.

x.div(y).plus(z).times(9).minus('1.234567801234567e+8').plus(976.54321).div('2598.11772')
x.sqrt().div(y).pow(3).gt(y.mod(z))    // true

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

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

The maximum number of decimal places and the rounding mode used to round the results of the div, sqrt and pow (with negative exponent) methods is determined by the value of the DP and RM properties of the Big number constructor.

The other methods always give the exact result.

(From v3.0.0, multiple Big number constructors can be created, see Change Log below.)

Big.DP = 10
Big.RM = 1

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

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

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

For further information see the API reference from the doc folder.

Test

The test directory contains the test scripts for each Big number method.

The tests can be run with Node or a browser.

To test a single method, from a command-line shell at the test directory, use e.g.

$ node toFixed

To test all the methods

$ node every-test

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

big-vs-number.html enables some of the methods of big.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.

big-vs-bigdecimal.html tests the performance of big.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 big.js against the GWT version of BigDecimal from the npm registry.

For example, to compare the time taken by the big.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

Build

I.e. minify.

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

uglifyjs -o ./big.min.js ./big.js

will create big.min.js.

TypeScript

The DefinitelyTyped project has a TypeScript definitions file for big.js.

The definitions file can be added to your project via the big.js.TypeScript.DefinitelyTyped NuGet package or via tsd.

tsd query big.js --action install

Any questions about the TypeScript definitions file should be addressed to the DefinitelyTyped project.

Feedback

Feedback is welcome.

Bugs/comments/questions? Open an issue, or email

Michael [e-mail]

Licence

See LICENCE.

Change Log

####5.0.1

• 13/10/17
• Correct Big.version number.

####5.0.0

• 13/10/17
• Return -0 from valueOf for negative zero.
• Refactor the methods which return a string.
• Amend error messaging.
• Update API document and change its colour scheme.
• Add Big.version.
• Remove bitcoin address.

####4.0.2

• 28/09/17
• Add big.mjs for use with Node.js with --experimental-modules flag.

####4.0.0

• 27/09/17
• Rename Big.E_POS to Big.PE, Big.E_NEG to Big.NE.
• Refactor error messaging.
• Throw if null is passed to toFixed etc.

####3.2.0

• 14/09/17 Aid ES6 import.

####3.1.3

• Minor documentation updates.

####3.1.2

• README typo.

####3.1.1

• API documentation update, including FAQ additions.

####3.1.0

• Renamed and exposed TO_EXP_NEG and TO_EXP_POS as Big.E_NEG and Big.E_POS.

####3.0.2

• Remove .npmignore, use files field in package.json instead.

####3.0.1

• Added sub, add and mul aliases.
• Clean-up after lint.

####3.0.0

• 10/12/14 Added multiple constructor functionality.
• No breaking changes or other additions, but a major code reorganisation, so v3 seemed appropiate.

####2.5.2

• 1/11/14 Added bower.json.

####2.5.1

• 8/06/14 Amend README requires.

####2.5.0

• 26/01/14 Added toJSON method so serialization uses toString.

####2.4.1

• 17/10/13 Conform signed zero to IEEEE 754 (2008).

####2.4.0

• 19/09/13 Throw instances of Error.

####2.3.0

• 16/09/13 Added cmp method.

####2.2.0

• 11/07/13 Added 'round up' mode.

####2.1.0

• 26/06/13 Allow e.g. .1 and 2..

####2.0.0

• 12/05/13 Added abs method and replaced cmp with eq, gt, gte, lt, and lte methods.

####1.0.1

• Changed default value of MAX_DP to 1E6

####1.0.0

• 7/11/2012 Initial release