An arbitrary-precision Decimal type for JavaScript.
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[](https://travis-ci.org/MikeMcl/decimal.js)
## Features
- Integers and floats
- Simple but full-featured API
- Replicates many of the methods of JavaScript's `Number.prototype` and `Math` objects
- Also handles hexadecimal, binary and octal values
- Supports serialization of Decimals to a compact base-88 format for transmission or persistence
- Faster, smaller, and perhaps easier to use than JavaScript versions of Java's BigDecimal
- No dependencies
- Wide platform compatibility: uses JavaScript 1.5 (ECMAScript 3) features only
- Comprehensive [documentation ](http://mikemcl.github.io/decimal.js/ ) and test set
The library is similar to [bignumber.js ](https://github.com/MikeMcl/bignumber.js/ ), but here
precision is specified in terms of significant digits instead of decimal places, and all
calculations are rounded to the precision (similar to Python's decimal module) rather than just
those involving division.
This library also adds the trigonometric functions, among others, and supports non-integer powers.
Another major difference is that this library enables multiple Decimal constructors to be created
each with their own configuration. This is, however, a significantly larger library than
*bignumber.js* and the even smaller [big.js ](https://github.com/MikeMcl/big.js/ ).
## Load
The library is the single JavaScript file *decimal.js* (or minified, *decimal.min.js* ).
It can be loaded using a script tag in an HTML document for the browser
< script src = 'path/to/decimal.js' > < / script >
or as a [Node.js ](http://nodejs.org ) module using `require` .
var Decimal = require('decimal');
For Node, the library is available from the [npm ](https://npmjs.org/ ) registry
$ npm install decimal.js
To load with AMD loader libraries such as [requireJS ](http://requirejs.org/ ):
require(['decimal'], function(Decimal) {
// Use Decimal here in local scope. No global Decimal.
});
## 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 object, `Decimal` , the constructor of Decimal instances.
It accepts a value of type number, string or Decimal.
x = new Decimal(123.4567)
y = new Decimal('123456.7e-3')
z = new Decimal(x)
x.equals(y) & & y.equals(z) & & x.equals(z) // true
A value can also be in binary, hexadecimal or octal if the appropriate prefix is included.
x = new Decimal('0xff.f') // '255.9375'
y = new Decimal('0b10101100') // '172'
z = x.plus(y) // '427.9375'
z.toBinary() // '0b110101011.1111'
z.toBinary(13) // '0b1.101010111111p+8'
A Decimal is immutable in the sense that it is not changed by its methods.
0.3 - 0.1 // 0.19999999999999998
x = new Decimal(0.3)
x.minus(0.1) // '0.2'
x // '0.3'
The methods that return a Decimal can be chained.
x.dividedBy(y).plus(z).times(9).floor()
x.times('1.23456780123456789e+9').plus(9876.5432321).dividedBy('4444562598.111772').ceil()
Many method names 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 Decimal(255.5)
x.toExponential(5) // '2.55500e+2'
x.toFixed(5) // '255.50000'
x.toPrecision(5) // '255.50'
and many of the methods of JavaScript's Math object are also replicated.
Decimal.sqrt('6.98372465832e+9823') // '8.3568682281821340204e+4911'
Decimal.pow(2, 0.0979843) // '1.0702770511687781839'
There are `isNaN` and `isFinite` methods, as `NaN` and `Infinity` are valid `Decimal` values,
x = new Decimal(NaN) // 'NaN'
y = new Decimal(Infinity) // 'Infinity'
x.isNaN() & & !y.isNaN() & & !x.isFinite() & & !y.isFinite() // true
and a `toFraction` method with an optional *maximum denominator* argument
z = new Decimal(355)
pi = z.dividedBy(113) // '3.1415929204'
pi.toFraction() // [ '7853982301', '2500000000' ]
pi.toFraction(1000) // [ '355', '113' ]
All calculations are rounded according to the number of significant digits and rounding mode
specified by the `precision` and `rounding` properties of the Decimal constructor.
As mentioned above, multiple Decimal constructors can be created, each with their own independent
configuration which applies to all Decimal numbers created from it.
// Set the precision and rounding of the default Decimal constructor
Decimal.config({ precision: 5, rounding: 4 })
// Create another Decimal constructor, optionally passing in a configuration object
Decimal10 = Decimal.clone({ precision: 10, rounding: 1 })
x = new Decimal(5)
y = new Decimal10(5)
x.div(3) // '1.6667'
y.div(3) // '1.666666666'
The value of a Decimal is stored in a floating point format in terms of its digits, exponent and sign.
x = new Decimal(-12345.67);
x.d // [ 12345, 6700000 ] digits (base 10000)
x.e // 4 exponent (base 10)
x.s // -1 sign
For further information see the [API ](http://mikemcl.github.io/decimal.js/ ) reference in the *doc* directory.
## Test
The library can be tested using Node.js or a browser.
The *test* directory contains the file *test.js* which runs all the tests when executed by Node, and the file *test.html* which runs all the tests when opened in a browser.
To run all the tests, from a command-line at the root directory using npm
$ npm test
or at the *test* directory using Node
$ node test
Each separate test module can also be executed individually, for example, at the *test/modules* directory
$ node toFraction
## Build
For Node, if [uglify-js ](https://github.com/mishoo/UglifyJS2 ) is installed
npm install uglify-js -g
then
npm run build
will create *decimal.min.js* , and a source map will also be added to the *doc* directory.
## Feedback
< a href = 'mailto:M8ch88l@gmail.com' > M8ch88l@gmail.com< / a >
BTC 16MjxmTB5EZxY5Uk9xyhfsu4n9gYxEJYkY
## Licence
MIT Expat.
See *LICENCE.md*
