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[6a3a178]1# big.js
2
3**A small, fast JavaScript library for arbitrary-precision decimal arithmetic.**
4
5The 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.
6
7## Features
8
9 - Faster, smaller and easier-to-use than JavaScript versions of Java's BigDecimal
10 - Only 5.9 KB minified and 2.7 KB gzipped
11 - Simple API
12 - Replicates the `toExponential`, `toFixed` and `toPrecision` methods of JavaScript's Number type
13 - Includes a `sqrt` method
14 - Stores values in an accessible decimal floating point format
15 - No dependencies
16 - Comprehensive [documentation](http://mikemcl.github.io/big.js/) and test set
17
18## Set up
19
20The library is the single JavaScript file *big.js* (or *big.min.js*, which is *big.js* minified).
21
22Browser:
23
24```html
25<script src='path/to/big.js'></script>
26```
27
28[Node.js](http://nodejs.org):
29
30```bash
31$ npm install big.js
32```
33
34```javascript
35const Big = require('big.js');
36```
37
38ES6 module:
39
40```javascript
41import Big from 'big.mjs';
42```
43## Use
44
45*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.*
46
47The library exports a single function, `Big`, the constructor of Big number instances.
48It accepts a value of type number, string or Big number object.
49
50 x = new Big(123.4567)
51 y = Big('123456.7e-3') // 'new' is optional
52 z = new Big(x)
53 x.eq(y) && x.eq(z) && y.eq(z) // true
54
55A Big number is immutable in the sense that it is not changed by its methods.
56
57 0.3 - 0.1 // 0.19999999999999998
58 x = new Big(0.3)
59 x.minus(0.1) // "0.2"
60 x // "0.3"
61
62The methods that return a Big number can be chained.
63
64 x.div(y).plus(z).times(9).minus('1.234567801234567e+8').plus(976.54321).div('2598.11772')
65 x.sqrt().div(y).pow(3).gt(y.mod(z)) // true
66
67Like JavaScript's Number type, there are `toExponential`, `toFixed` and `toPrecision` methods.
68
69 x = new Big(255.5)
70 x.toExponential(5) // "2.55500e+2"
71 x.toFixed(5) // "255.50000"
72 x.toPrecision(5) // "255.50"
73
74The arithmetic methods always return the exact result except `div`, `sqrt` and `pow`
75(with negative exponent), as these methods involve division.
76
77The 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.
78
79 Big.DP = 10
80 Big.RM = 1
81
82 x = new Big(2);
83 y = new Big(3);
84 z = x.div(y) // "0.6666666667"
85 z.sqrt() // "0.8164965809"
86 z.pow(-3) // "3.3749999995"
87 z.times(z) // "0.44444444448888888889"
88 z.times(z).round(10) // "0.4444444445"
89
90Multiple Big number constructors can be created, each with an independent configuration.
91
92The value of a Big number is stored in a decimal floating point format in terms of a coefficient, exponent and sign.
93
94 x = new Big(-123.456);
95 x.c // [1,2,3,4,5,6] coefficient (i.e. significand)
96 x.e // 2 exponent
97 x.s // -1 sign
98
99For further information see the [API](http://mikemcl.github.io/big.js/) reference from the *doc* folder.
100
101## Test
102
103The *test* directory contains the test scripts for each Big number method.
104
105The tests can be run with Node.js or a browser.
106
107To run all the tests
108
109 $ npm test
110
111To test a single method
112
113 $ node test/toFixed
114
115For the browser, see *single-test.html* and *every-test.html* in the *test/browser* directory.
116
117*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.
118
119## Performance
120
121The *perf* directory contains two legacy applications and a *lib* directory containing the BigDecimal libraries used by both.
122
123*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.
124
125* [GWT: java.math.BigDecimal](https://github.com/iriscouch/bigdecimal.js)
126* [ICU4J: com.ibm.icu.math.BigDecimal](https://github.com/dtrebbien/BigDecimal.js)
127
128The 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.
129
130*bigtime.js* is a Node.js command-line application which tests the performance of big.js against the GWT version of
131BigDecimal from the npm registry.
132
133For example, to compare the time taken by the big.js `plus` method and the BigDecimal `add` method
134
135 $ node bigtime plus 10000 40
136
137This will time 10000 calls to each, using operands of up to 40 random digits and will check that the results match.
138
139For help
140
141 $ node bigtime -h
142
143## Build
144
145If [uglify-js](https://github.com/mishoo/UglifyJS2) is installed globally
146
147 $ npm install uglify-js -g
148
149then
150
151 $ npm run build
152
153will create *big.min.js*.
154
155## TypeScript
156
157The [DefinitelyTyped](https://github.com/borisyankov/DefinitelyTyped) project has a Typescript type definitions file for big.js.
158
159 $ npm install @types/big.js
160
161Any questions about the TypeScript type definitions file should be addressed to the DefinitelyTyped project.
162
163## Feedback
164
165Bugs/comments/questions?
166
167Open an issue, or email <a href="mailto:M8ch88l@gmail.com">Michael</a>
168
169## Licence
170
171[MIT](LICENCE)
172
173## Contributors
174
175This project exists thanks to all the people who contribute. [[Contribute](CONTRIBUTING.md)].
176<a href="graphs/contributors"><img src="https://opencollective.com/bigjs/contributors.svg?width=890&button=false" /></a>
177
178
179## Backers
180
181Thank you to all our backers! 🙏 [[Become a backer](https://opencollective.com/bigjs#backer)]
182
183<a href="https://opencollective.com/bigjs#backers" target="_blank"><img src="https://opencollective.com/bigjs/backers.svg?width=890"></a>
184
185
186## Sponsors
187
188Support 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)]
189
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