whateat/程序代码/后端服务器/eatwhat-server-local/node_modules/_bignumber.js@9.0.0@bignumber.js/README.md

![bignumber.js](https://raw.githubusercontent.com/MikeMcl/bignumber.js/gh-pages/bignumberjs.png)

A JavaScript library for arbitrary-precision decimal and non-decimal arithmetic.

[![Build Status](https://travis-ci.org/MikeMcl/bignumber.js.svg)](https://travis-ci.org/MikeMcl/bignumber.js)

<br />

## Features

  - Integers and decimals
  - Simple API but full-featured
  - Faster, smaller, and perhaps easier to use than JavaScript versions of Java's BigDecimal
  - 8 KB minified and gzipped
  - Replicates the `toExponential`, `toFixed`, `toPrecision` and `toString` methods of JavaScript's Number type
  - Includes a `toFraction` and a correctly-rounded `squareRoot` method
  - Supports cryptographically-secure pseudo-random number generation
  - No dependencies
  - Wide platform compatibility: uses JavaScript 1.5 (ECMAScript 3) features only
  - Comprehensive [documentation](http://mikemcl.github.io/bignumber.js/) and test set

![API](https://raw.githubusercontent.com/MikeMcl/bignumber.js/gh-pages/API.png)

If a smaller and simpler library is required see [big.js](https://github.com/MikeMcl/big.js/).
It's less than half the size but only works with decimal numbers and only has half the methods.
It also does not allow `NaN` or `Infinity`, or have the configuration options of this library.

See also [decimal.js](https://github.com/MikeMcl/decimal.js/), which among other things adds support for non-integer powers, and performs all operations to a specified number of significant digits.

## Load

The library is the single JavaScript file *bignumber.js* (or minified, *bignumber.min.js*).

Browser:

```html
<script src='path/to/bignumber.js'></script>
```

[Node.js](http://nodejs.org):

```bash
$ npm install bignumber.js
```

```javascript
const BigNumber = require('bignumber.js');
```

ES6 module:

```javascript
import BigNumber from "./bignumber.mjs"
```

AMD loader libraries such as [requireJS](http://requirejs.org/):

```javascript
require(['bignumber'], function(BigNumber) {
    // Use BigNumber here in local scope. No global BigNumber.
});
```

## Use

The library exports a single constructor function, [`BigNumber`](http://mikemcl.github.io/bignumber.js/#bignumber), which accepts a value of type Number, String or BigNumber,

```javascript
let x = new BigNumber(123.4567);
let y = BigNumber('123456.7e-3');
let z = new BigNumber(x);
x.isEqualTo(y) && y.isEqualTo(z) && x.isEqualTo(z);      // true
```

To get the string value of a BigNumber use [`toString()`](http://mikemcl.github.io/bignumber.js/#toS) or [`toFixed()`](http://mikemcl.github.io/bignumber.js/#toFix). Using `toFixed()` prevents exponential notation being returned, no matter how large or small the value.

```javascript
let x = new BigNumber('1111222233334444555566');
x.toString();                       // "1.111222233334444555566e+21"
x.toFixed();                        // "1111222233334444555566"
```

If the limited precision of Number values is not well understood, it is recommended to create BigNumbers from String values rather than Number values to avoid a potential loss of precision.

*In all further examples below, `let`, 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.*

```javascript
// Precision loss from using numeric literals with more than 15 significant digits.
new BigNumber(1.0000000000000001)         // '1'
new BigNumber(88259496234518.57)          // '88259496234518.56'
new BigNumber(99999999999999999999)       // '100000000000000000000'

// Precision loss from using numeric literals outside the range of Number values.
new BigNumber(2e+308)                     // 'Infinity'
new BigNumber(1e-324)                     // '0'

// Precision loss from the unexpected result of arithmetic with Number values.
new BigNumber(0.7 + 0.1)                  // '0.7999999999999999'
```

When creating a BigNumber from a Number, note that a BigNumber is created from a Number's decimal `toString()` value not from its underlying binary value. If the latter is required, then pass the Number's `toString(2)` value and specify base 2.

```javascript
new BigNumber(Number.MAX_VALUE.toString(2), 2)
```

BigNumbers can be created from values in bases from 2 to 36. See [`ALPHABET`](http://mikemcl.github.io/bignumber.js/#alphabet) to extend this range.

```javascript
a = new BigNumber(1011, 2)          // "11"
b = new BigNumber('zz.9', 36)       // "1295.25"
c = a.plus(b)                       // "1306.25"
```

Performance is better if base 10 is NOT specified for decimal values. Only specify base 10 when it is desired that the number of decimal places of the input value be limited to the current [`DECIMAL_PLACES`](http://mikemcl.github.io/bignumber.js/#decimal-places) setting.

A BigNumber is immutable in the sense that it is not changed by its methods.

```javascript
0.3 - 0.1                           // 0.19999999999999998
x = new BigNumber(0.3)
x.minus(0.1)                        // "0.2"
x                                   // "0.3"
```

The methods that return a BigNumber can be chained.

```javascript
x.dividedBy(y).plus(z).times(9)
x.times('1.23456780123456789e+9').plus(9876.5432321).dividedBy('4444562598.111772').integerValue()
```

Some of the longer method names have a shorter alias.

```javascript
x.squareRoot().dividedBy(y).exponentiatedBy(3).isEqualTo(x.sqrt().div(y).pow(3))    // true
x.modulo(y).multipliedBy(z).eq(x.mod(y).times(z))                                   // true
```

As with JavaScript's Number type, there are [`toExponential`](http://mikemcl.github.io/bignumber.js/#toE), [`toFixed`](http://mikemcl.github.io/bignumber.js/#toFix) and [`toPrecision`](http://mikemcl.github.io/bignumber.js/#toP) methods.

```javascript
x = new BigNumber(255.5)
x.toExponential(5)                  // "2.55500e+2"
x.toFixed(5)                        // "255.50000"
x.toPrecision(5)                    // "255.50"
x.toNumber()                        //  255.5
```

 A base can be specified for [`toString`](http://mikemcl.github.io/bignumber.js/#toS). Performance is better if base 10 is NOT specified, i.e. use `toString()` not `toString(10)`. Only specify base 10 when it is desired that the number of decimal places be limited to the current [`DECIMAL_PLACES`](http://mikemcl.github.io/bignumber.js/#decimal-places) setting.

 ```javascript
 x.toString(16)                     // "ff.8"
 ```

There is a [`toFormat`](http://mikemcl.github.io/bignumber.js/#toFor) method which may be useful for internationalisation.

```javascript
y = new BigNumber('1234567.898765')
y.toFormat(2)                       // "1,234,567.90"
```

The maximum number of decimal places of the result of an operation involving division (i.e. a division, square root, base conversion or negative power operation) is set using the `set` or `config` method of the `BigNumber` constructor.

The other arithmetic operations always give the exact result.

```javascript
BigNumber.set({ DECIMAL_PLACES: 10, ROUNDING_MODE: 4 })

x = new BigNumber(2)
y = new BigNumber(3)
z = x.dividedBy(y)                        // "0.6666666667"
z.squareRoot()                            // "0.8164965809"
z.exponentiatedBy(-3)                     // "3.3749999995"
z.toString(2)                             // "0.1010101011"
z.multipliedBy(z)                         // "0.44444444448888888889"
z.multipliedBy(z).decimalPlaces(10)       // "0.4444444445"
```

There is a [`toFraction`](http://mikemcl.github.io/bignumber.js/#toFr) method with an optional *maximum denominator* argument

```javascript
y = new BigNumber(355)
pi = y.dividedBy(113)               // "3.1415929204"
pi.toFraction()                     // [ "7853982301", "2500000000" ]
pi.toFraction(1000)                 // [ "355", "113" ]
```

and [`isNaN`](http://mikemcl.github.io/bignumber.js/#isNaN) and [`isFinite`](http://mikemcl.github.io/bignumber.js/#isF) methods, as `NaN` and `Infinity` are valid `BigNumber` values.

```javascript
x = new BigNumber(NaN)                                           // "NaN"
y = new BigNumber(Infinity)                                      // "Infinity"
x.isNaN() && !y.isNaN() && !x.isFinite() && !y.isFinite()        // true
```

The value of a BigNumber is stored in a decimal floating point format in terms of a coefficient, exponent and sign.

```javascript
x = new BigNumber(-123.456);
x.c                                 // [ 123, 45600000000000 ]  coefficient (i.e. significand)
x.e                                 // 2                        exponent
x.s                                 // -1                       sign
```

For advanced usage, multiple BigNumber constructors can be created, each with their own independent configuration.

```javascript
// Set DECIMAL_PLACES for the original BigNumber constructor
BigNumber.set({ DECIMAL_PLACES: 10 })

// Create another BigNumber constructor, optionally passing in a configuration object
BN = BigNumber.clone({ DECIMAL_PLACES: 5 })

x = new BigNumber(1)
y = new BN(1)

x.div(3)                            // '0.3333333333'
y.div(3)                            // '0.33333'
```

For further information see the [API](http://mikemcl.github.io/bignumber.js/) reference in the *doc* directory.

## Test

The *test/modules* directory contains the test scripts for each method.

The tests can be run with Node.js or a browser. For Node.js use

    $ npm test

or

    $ node test/test

To test a single method, use, for example

    $ node test/methods/toFraction

For the browser, open *test/test.html*.

## Build

For Node, if [uglify-js](https://github.com/mishoo/UglifyJS2) is installed

    npm install uglify-js -g

then

    npm run build

will create *bignumber.min.js*.

A source map will also be created in the root directory.

## Feedback

Open an issue, or email

Michael

<a href="mailto:M8ch88l@gmail.com">M8ch88l@gmail.com</a>

## Licence

The MIT Licence.

See [LICENCE](https://github.com/MikeMcl/bignumber.js/blob/master/LICENCE).