Building-Blockchain-Projects:Packt发布的用于构建区块链项目的代码存储库

 A JavaScript library for arbitrary-precision decimal and non-decimal arithmetic. [](https://travis-ci.org/MikeMcl/bignumber.js) <br /> ## Features - Faster, smaller, and perhaps easier to use than JavaScript versions of Java's BigDecimal - 8 KB minified and gzipped - Simple API but full-featured - Works with numbers with or without fraction digits in bases from 2 to 64 inclusive - 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  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*). ```html <script src='relative/path/to/bignumber.js'></script> ``` For [Node.js](http://nodejs.org) or [io.js](https://iojs.org/en/index.html), the library is available from the [npm](https://npmjs.org/) registry $ npm install bignumber.js ```javascript var BigNumber = require('bignumber.js'); ``` To load with AMD loader libraries such as [requireJS](http://requirejs.org/): ```javascript require(['path/to/bignumber'], function(BigNumber) { // Use BigNumber here in local scope. No global BigNumber. }); ``` ## 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: `BigNumber`, the constructor of BigNumber instances. It accepts a value of type number *(up to 15 significant digits only)*, string or BigNumber object, ```javascript x = new BigNumber(123.4567) y = BigNumber('123456.7e-3') z = new BigNumber(x) x.equals(y) && y.equals(z) && x.equals(z) // true ``` and a base from 2 to 64 inclusive can be specified. ```javascript x = new BigNumber(1011, 2) // "11" y = new BigNumber('zz.9', 36) // "1295.25" z = x.plus(y) // "1306.25" ``` 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).floor() x.times('1.23456780123456789e+9').plus(9876.5432321).dividedBy('4444562598.111772').ceil() ``` Many method names have a shorter alias. ```javascript 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 ```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 ``` and a base can be specified for `toString`. ```javascript x.toString(16) // "ff.8" ``` There is also a `toFormat` 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 `config` method of the `BigNumber` constructor. The other arithmetic operations always give the exact result. ```javascript BigNumber.config({ DECIMAL_PLACES: 10, ROUNDING_MODE: 4 }) // Alternatively, BigNumber.config( 10, 4 ); x = new BigNumber(2); y = new BigNumber(3); z = x.div(y) // "0.6666666667" z.sqrt() // "0.8164965809" z.pow(-3) // "3.3749999995" z.toString(2) // "0.1010101011" z.times(z) // "0.44444444448888888889" z.times(z).round(10) // "0.4444444445" ``` There is a `toFraction` 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` and `isFinite` 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 ``` Multiple BigNumber constructors can be created, each with their own independent configuration which applies to all BigNumber's created from it. ```javascript // Set DECIMAL_PLACES for the original BigNumber constructor BigNumber.config({ DECIMAL_PLACES: 10 }) // Create another BigNumber constructor, optionally passing in a configuration object BN = BigNumber.another({ DECIMAL_PLACES: 5 }) x = new BigNumber(1) y = new BN(1) x.div(3) // '0.3333333333' y.div(3) // '0.33333' ``` For futher information see the [API](http://mikemcl.github.io/bignumber.js/) reference in the *doc* directory. ## Test The *test* directory contains the test scripts for each method. The tests can be run with Node or a browser. For Node use $ npm test or $ node test/every-test To test a single method, e.g. $ node test/toFraction For the browser, see *every-test.html* and *single-test.html* in the *test/browser* directory. *bignumber-vs-number.html* enables some of the methods of bignumber.js to be compared with those of JavaScript's number type. ## Versions This is version 2.x.x of the library, for version 1.x.x see the tagged releases or switch to the 'original' branch. The advantages of version 2 are that it is considerably faster for numbers with many digits and that there are a some added methods (see Change Log below). The disadvantages are more lines of code and increased code complexity, and the loss of simplicity in no longer having the coefficient of a BigNumber stored in base 10. The 'original' version will continue to be supported. ## Performance See the [README](https://github.com/MikeMcl/bignumber.js/tree/master/perf) in the *perf* directory. ## Build For Node, if [uglify-js](https://github.com/mishoo/UglifyJS2) is installed npm install uglify-js -g then npm r