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.
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"}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 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 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.
A small, fast JavaScript library for arbitrary-precision decimal arithmetic.
The little sister to bignumber.js and decimal.js. See here for some notes on the difference between them.
toExponential, toFixed and toPrecision methods of JavaScript's Number typesqrt methodNode.js users can install from the npm registry using
$ npm install --save big.js
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');
If using an ES6 transpiler, or Node.js with the --experimental-modules flag, try
import Big from 'big.js';
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 arithmetic methods always return the exact result except div, sqrt and pow
(with negative exponent), as these are the methods which involve division.
The maximum number of decimal places and the rounding mode used to round the results of these methods is determined by the value of the DP and RM properties of the Big number constructor.
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"
Multiple Big number constructors can be created, each with an independent configuration.
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.
The test directory contains the test scripts for each Big number method.
The tests can be run with Node.js or a browser.
To run all the tests
$ npm test
To test a single method
$ node test/toFixed
For the browser, see single-test.html and every-test.html in the test/browser directory.
big-vs-number.html is a simple application that enables some of the methods of big.js to be compared with those of JavaScript's Number type.
The perf directory contains two old 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 BigDecimal in the npm registry is the GWT version. Despite its seeming popularity I have found it to have some serious bugs, see the Node.js script perf/lib/bigdecimal_GWT/bugs.js for examples of flaws in its remainder, divide and compareTo methods.
bigtime.js is a Node.js 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
If uglify-js is installed globally
$ npm install uglify-js -g
then
$ npm run build
will create big.min.js.
The DefinitelyTyped project has a Typescript type definitions file for big.js.
$ npm install --save @types/big.js
Any questions about the TypeScript type definitions file should be addressed to the DefinitelyTyped project.
Bugs/comments/questions?
Open an issue, or email Michael
FAQs
A small, fast, easy-to-use library for arbitrary-precision decimal arithmetic
We found that big.js demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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