- Only 5.9 KB minified and 2.7 KB gzipped
- Simple API
- Replicates the
- Includes a
- Stores values in an accessible decimal floating point format
- No dependencies
- Comprehensive documentation and test set
$ npm install big.js
const Big = require('big.js');
import Big from './big.mjs';
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
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
(with negative exponent), as these methods 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
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.
The perf directory contains two legacy applications and a lib directory containing the BigDecimal libraries used by both.
The BigDecimal in the npm registry is the GWT version. It has some 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
$ 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.
$ node bigtime -h
If uglify-js is installed globally
$ npm install uglify-js -g
$ npm run build
will create big.min.js.
The DefinitelyTyped project has a Typescript type definitions file for big.js.
$ npm install --save-dev @types/big.js
Any questions about the TypeScript type definitions file should be addressed to the DefinitelyTyped project.
Open an issue, or email Michael
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