mirror of
https://github.com/MikeMcl/decimal.js.git
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220 lines
7.3 KiB
Markdown
220 lines
7.3 KiB
Markdown
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An arbitrary-precision Decimal type for JavaScript.
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<br>
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## Features
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- Faster, smaller, and perhaps easier to use than JavaScript versions of Java's BigDecimal
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- Simple API but full-featured
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- Replicates the `toExponential`, `toFixed`, `toPrecision` and `toString` methods of JavaScript's Number type
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- Includes a `toFraction` and correctly-rounded `exp`, `ln`, `log` and `sqrt` functions
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- Supports non-integer powers (although performance is limited)
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- Works with numbers with or without fraction digits in bases from 2 to 64 inclusive
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- Stores values in an accessible decimal floating-point format
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- No dependencies
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- Wide platform compatibility: uses JavaScript 1.5 (ECMAScript 3) features only
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- Comprehensive [documentation](http://mikemcl.github.io/decimal.js/) and test set
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- 8 KB minified and gzipped
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The library is similar to [bignumber.js](https://github.com/MikeMcl/bignumber.js/), but here
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precision is specified in terms of significant digits instead of decimal places, and all
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calculations are rounded to the precision (similar to Python's decimal module) rather than just
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those involving division.
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This library also adds `exp`, `ln` and `log` functions, among others, and supports non-integer powers.
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Another major difference is that this library enables multiple Decimal constructors to be created
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each with their own configuration (e.g. precision and range). This is, however, a significantly
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larger library than *bignumber.js* and the even smaller [big.js](https://github.com/MikeMcl/big.js/).
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## Load
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The library is the single JavaScript file *decimal.js* (or minified, *decimal.min.js*).
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It can be loaded via a script tag in an HTML document for the browser
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<script src='./relative/path/to/decimal.js'></script>
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or as a CommonJS, [Node.js](http://nodejs.org) or AMD module using `require`.
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For Node, the library is also available from the [npm](https://npmjs.org/) registry
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$ npm install decimal.js
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To load with AMD loader libraries such as [requireJS](http://requirejs.org/):
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require(['decimal'], function(Decimal) {
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// Use Decimal here in local scope. No global Decimal.
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});
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## Use
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*In all examples below, `var`, semicolons and `toString` calls are not shown.
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If a commented-out value is in quotes it means `toString` has been called on the preceding expression.*
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The library exports a single function object, `Decimal`, the constructor of Decimal numbers.
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It accepts a value of type number *(up to 15 significant digits only)*, string or Decimal.
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x = new Decimal(123.4567)
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y = new Decimal('123456.7e-3')
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z = new Decimal(x)
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x.equals(y) && y.equals(z) && x.equals(z) // true
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A base from 2 to 36 inclusive can also be specified.
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x = new Decimal(1011, 2) // '11'
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y = new Decimal('zz.9', 36) // '1295.25'
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z = x.plus(y) // '1306.25'
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A Decimal is immutable in the sense that it is not changed by its methods.
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0.3 - 0.1 // 0.19999999999999998
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x = new Decimal(0.3)
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x.minus(0.1) // '0.2'
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x // '0.3'
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The methods that return a Decimal can be chained.
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x.dividedBy(y).plus(z).times(9).floor()
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x.times('1.23456780123456789e+9').plus(9876.5432321).dividedBy('4444562598.111772').ceil()
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Many method names have a shorter alias.
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x.squareRoot().dividedBy(y).toPower(3).equals(x.sqrt().div(y).pow(3)) // true
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x.cmp(y.mod(z).neg()) == 1 && x.comparedTo(y.modulo(z).negated()) == 1 // true
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Like JavaScript's Number type, there are `toExponential`, `toFixed` and `toPrecision` methods
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x = new Decimal(255.5)
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x.toExponential(5) // '2.55500e+2'
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x.toFixed(5) // '255.50000'
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x.toPrecision(5) // '255.50'
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and a base can be specified for `toString`.
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x.toString(16) // 'ff.8'
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There is a `toFraction` method with an optional *maximum denominator* argument
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y = new Decimal(355)
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pi = y.dividedBy(113) // '3.1415929204'
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pi.toFraction() // [ '7853982301', '2500000000' ]
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pi.toFraction(1000) // [ '355', '113' ]
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and `isNaN` and `isFinite` methods, as `NaN` and `Infinity` are valid `Decimal` values.
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x = new Decimal(NaN) // 'NaN'
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y = new Decimal(Infinity) // 'Infinity'
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x.isNaN() && !y.isNaN() && !x.isFinite() && !y.isFinite() // true
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All calculations are rounded to the number of significant digits specified by the `precision` property
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of the Decimal constructor and rounded using the rounding mode specified by the `rounding` property.
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As mentioned above, multiple Decimal constructors can be created, each with their own independent
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configuration which applies to all Decimal numbers created from it.
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Decimal.config({ precision: 5, rounding: 4 })
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// constructor is a factory method and it can also accept a configuration object
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Decimal10 = Decimal.constructor({ precision: 10, rounding: 1 })
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x = new Decimal(5)
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y = new Decimal10(5)
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x.div(3) // '1.6667'
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y.div(3) // '1.666666666'
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Decimal.precision // 5
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Decimal10.precision // 10
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Many of the methods of JavaScript's Math object are also replicated
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Decimal.sqrt('6.98372465832e+9823') // '8.3568682281821340204e+4911'
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Decimal.pow(2, 0.0979843) // '1.0702770511687781839'
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The value of a Decimal is stored in a decimal floating point format in terms of a coefficient, exponent and sign.
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x = new Decimal(-123.456);
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x.c // '1,2,3,4,5,6' coefficient (i.e. significand)
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x.e // 2 exponent
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x.s // -1 sign
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For further information see the [API](http://mikemcl.github.io/decimal.js/) reference in the *doc* directory.
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## Test
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The *test* directory contains the test scripts for each method.
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The tests can be run with Node or a browser.
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To test a single method use, from a command-line shell in the root directory, for example
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$ node test/toFraction
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To test all the methods
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$ node test/every-test
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or
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$ npm test
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For the browser, see *single-test.html* and *every-test.html* in the *test/browser* directory,
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## Build
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For Node, if [uglify-js](https://github.com/mishoo/UglifyJS2) is installed
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npm install uglify-js -g
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then
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npm run build
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will create *decimal.min.js*.
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The *decimal.min.js* already present was created with *Microsoft Ajax Minifier 5.8*.
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## Feedback
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Open an issue, or email
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Michael <a href='mailto:M8ch88l@gmail.com'>M8ch88l@gmail.com</a>
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[Bitcoin](https://bitcoin.org/en/getting-started) donations gratefully received:
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**1PjzRBjGJycti49AXTiKsdC4PRCnTbyUyf**
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Thank you
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## Licence
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MIT Expat.
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See LICENCE.
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## Change Log
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####2.0.3
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* 8/05/2014 Fix NaN toNumber
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####2.0.2
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* 30/04/2014 Correct doc links
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####2.0.1
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* 10/04/2014 Update npmignore
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####2.0.0
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* 10/04/2014 Add `toSignificantDigits`
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* Remove `toInteger`
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* No arguments to `ceil`, `floor`, `round` and `trunc`
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####1.0.1
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* 07/04/2014 Minor documentation clean-up
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####1.0.0
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* 02/04/2014 Initial release
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