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202 lines
8.0 KiB
202 lines
8.0 KiB
# big.js
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**A small, fast JavaScript library for arbitrary-precision decimal arithmetic.**
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The little sister to [bignumber.js](https://github.com/MikeMcl/bignumber.js/) and [decimal.js](https://github.com/MikeMcl/decimal.js/). See [here](https://github.com/MikeMcl/big.js/wiki) for some notes on the difference between them.
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## Features
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- Faster, smaller and easier-to-use than JavaScript versions of Java's BigDecimal
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- Only 5.9 KB minified and 2.7 KB gzipped
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- Simple API
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- Replicates the `toExponential`, `toFixed` and `toPrecision` methods of JavaScript's Number type
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- Includes a `sqrt` method
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- Stores values in an accessible decimal floating point format
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- No dependencies
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- Comprehensive [documentation](http://mikemcl.github.io/big.js/) and test set
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## Set up
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The library is the single JavaScript file *big.js* (or *big.min.js*, which is *big.js* minified).
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Browser:
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```html
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<script src='path/to/big.js'></script>
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```
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[Node.js](http://nodejs.org):
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```bash
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$ npm install big.js
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```
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```javascript
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const Big = require('big.js');
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```
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ES6 module:
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```javascript
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import Big from 'big.mjs';
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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. 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, `Big`, the constructor of Big number instances.
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It accepts a value of type number, string or Big number object.
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x = new Big(123.4567)
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y = Big('123456.7e-3') // 'new' is optional
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z = new Big(x)
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x.eq(y) && x.eq(z) && y.eq(z) // true
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A Big number 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 Big(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 Big number can be chained.
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x.div(y).plus(z).times(9).minus('1.234567801234567e+8').plus(976.54321).div('2598.11772')
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x.sqrt().div(y).pow(3).gt(y.mod(z)) // true
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Like JavaScript's Number type, there are `toExponential`, `toFixed` and `toPrecision` methods.
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x = new Big(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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The arithmetic methods always return the exact result except `div`, `sqrt` and `pow`
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(with negative exponent), as these methods involve division.
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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.
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Big.DP = 10
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Big.RM = 1
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x = new Big(2);
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y = new Big(3);
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z = x.div(y) // "0.6666666667"
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z.sqrt() // "0.8164965809"
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z.pow(-3) // "3.3749999995"
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z.times(z) // "0.44444444448888888889"
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z.times(z).round(10) // "0.4444444445"
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Multiple Big number constructors can be created, each with an independent configuration.
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The value of a Big number is stored in a decimal floating point format in terms of a coefficient, exponent and sign.
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x = new Big(-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/big.js/) reference from the *doc* folder.
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## Test
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The *test* directory contains the test scripts for each Big number method.
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The tests can be run with Node.js or a browser.
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To run all the tests
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$ npm test
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To test a single method
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$ node test/toFixed
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For the browser, see *single-test.html* and *every-test.html* in the *test/browser* directory.
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*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.
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## Performance
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The *perf* directory contains two legacy applications and a *lib* directory containing the BigDecimal libraries used by both.
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*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.
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* [GWT: java.math.BigDecimal](https://github.com/iriscouch/bigdecimal.js)
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* [ICU4J: com.ibm.icu.math.BigDecimal](https://github.com/dtrebbien/BigDecimal.js)
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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.
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*bigtime.js* is a Node.js command-line application which tests the performance of big.js against the GWT version of
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BigDecimal from the npm registry.
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For example, to compare the time taken by the big.js `plus` method and the BigDecimal `add` method
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$ node bigtime plus 10000 40
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This will time 10000 calls to each, using operands of up to 40 random digits and will check that the results match.
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For help
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$ node bigtime -h
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## Build
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If [uglify-js](https://github.com/mishoo/UglifyJS2) is installed globally
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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 *big.min.js*.
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## TypeScript
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The [DefinitelyTyped](https://github.com/borisyankov/DefinitelyTyped) project has a Typescript type definitions file for big.js.
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$ npm install @types/big.js
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Any questions about the TypeScript type definitions file should be addressed to the DefinitelyTyped project.
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## Feedback
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Bugs/comments/questions?
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Open an issue, or email <a href="mailto:M8ch88l@gmail.com">Michael</a>
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## Licence
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[MIT](LICENCE)
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## Contributors
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This project exists thanks to all the people who contribute. [[Contribute](CONTRIBUTING.md)].
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<a href="graphs/contributors"><img src="https://opencollective.com/bigjs/contributors.svg?width=890&button=false" /></a>
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## Backers
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Thank you to all our backers! 🙏 [[Become a backer](https://opencollective.com/bigjs#backer)]
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<a href="https://opencollective.com/bigjs#backers" target="_blank"><img src="https://opencollective.com/bigjs/backers.svg?width=890"></a>
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## Sponsors
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Support this project by becoming a sponsor. Your logo will show up here with a link to your website. [[Become a sponsor](https://opencollective.com/bigjs#sponsor)]
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<a href="https://opencollective.com/bigjs/sponsor/0/website" target="_blank"><img src="https://opencollective.com/bigjs/sponsor/0/avatar.svg"></a>
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