You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
246 lines
8.4 KiB
246 lines
8.4 KiB
 |
|
|
|
An arbitrary-precision Decimal type for JavaScript. |
|
|
|
[](https://www.npmjs.com/package/decimal.js) |
|
[](https://www.npmjs.com/package/decimal.js) |
|
[](https://travis-ci.org/MikeMcl/decimal.js) |
|
[](https://cdnjs.com/libraries/decimal.js) |
|
|
|
<br> |
|
|
|
## Features |
|
|
|
- Integers and floats |
|
- Simple but full-featured API |
|
- Replicates many of the methods of JavaScript's `Number.prototype` and `Math` objects |
|
- Also handles hexadecimal, binary and octal values |
|
- Faster, smaller, and perhaps easier to use than JavaScript versions of Java's BigDecimal |
|
- No dependencies |
|
- Wide platform compatibility: uses JavaScript 1.5 (ECMAScript 3) features only |
|
- Comprehensive [documentation](https://mikemcl.github.io/decimal.js/) and test set |
|
- Used under the hood by [math.js](https://github.com/josdejong/mathjs) |
|
- Includes a TypeScript declaration file: *decimal.d.ts* |
|
|
|
 |
|
|
|
The library is similar to [bignumber.js](https://github.com/MikeMcl/bignumber.js/), but here |
|
precision is specified in terms of significant digits rather than decimal places, and all |
|
calculations are rounded to the precision (similar to Python's decimal module) rather than just |
|
those involving division. |
|
|
|
This library also adds the trigonometric functions, among others, and supports non-integer powers, |
|
which makes it a significantly larger library than *bignumber.js* and the even smaller |
|
[big.js](https://github.com/MikeMcl/big.js/). |
|
|
|
For a lighter version of this library without the trigonometric functions see |
|
[decimal.js-light](https://github.com/MikeMcl/decimal.js-light/). |
|
|
|
## Load |
|
|
|
The library is the single JavaScript file *decimal.js* or ES module *decimal.mjs*. |
|
|
|
Browser: |
|
|
|
```html |
|
<script src='path/to/decimal.js'></script> |
|
|
|
<script type="module"> |
|
import Decimal from './path/to/decimal.mjs'; |
|
... |
|
</script> |
|
``` |
|
|
|
[Node.js](https://nodejs.org): |
|
|
|
```bash |
|
npm install decimal.js |
|
``` |
|
```js |
|
const Decimal = require('decimal.js'); |
|
|
|
import Decimal from 'decimal.js'; |
|
|
|
import {Decimal} from 'decimal.js'; |
|
``` |
|
|
|
## Use |
|
|
|
*In all examples below, 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 constructor function, `Decimal`, which expects a single argument that is a number, string or Decimal instance. |
|
|
|
```js |
|
x = new Decimal(123.4567) |
|
y = new Decimal('123456.7e-3') |
|
z = new Decimal(x) |
|
x.equals(y) && y.equals(z) && x.equals(z) // true |
|
``` |
|
|
|
If using values with more than a few digits, it is recommended to pass strings rather than numbers to avoid a potential loss of precision. |
|
|
|
```js |
|
// Precision loss from using numeric literals with more than 15 significant digits. |
|
new Decimal(1.0000000000000001) // '1' |
|
new Decimal(88259496234518.57) // '88259496234518.56' |
|
new Decimal(99999999999999999999) // '100000000000000000000' |
|
|
|
// Precision loss from using numeric literals outside the range of Number values. |
|
new Decimal(2e+308) // 'Infinity' |
|
new Decimal(1e-324) // '0' |
|
|
|
// Precision loss from the unexpected result of arithmetic with Number values. |
|
new Decimal(0.7 + 0.1) // '0.7999999999999999' |
|
``` |
|
|
|
As with JavaScript numbers, strings can contain underscores as separators to improve readability. |
|
|
|
```js |
|
x = new Decimal('2_147_483_647') |
|
``` |
|
|
|
String values in binary, hexadecimal or octal notation are also accepted if the appropriate prefix is included. |
|
|
|
```js |
|
x = new Decimal('0xff.f') // '255.9375' |
|
y = new Decimal('0b10101100') // '172' |
|
z = x.plus(y) // '427.9375' |
|
|
|
z.toBinary() // '0b110101011.1111' |
|
z.toBinary(13) // '0b1.101010111111p+8' |
|
|
|
// Using binary exponential notation to create a Decimal with the value of `Number.MAX_VALUE`. |
|
x = new Decimal('0b1.1111111111111111111111111111111111111111111111111111p+1023') |
|
// '1.7976931348623157081e+308' |
|
``` |
|
|
|
Decimal instances are immutable in the sense that they are not changed by their methods. |
|
|
|
```js |
|
0.3 - 0.1 // 0.19999999999999998 |
|
x = new Decimal(0.3) |
|
x.minus(0.1) // '0.2' |
|
x // '0.3' |
|
``` |
|
|
|
The methods that return a Decimal can be chained. |
|
|
|
```js |
|
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. |
|
|
|
```js |
|
x.squareRoot().dividedBy(y).toPower(3).equals(x.sqrt().div(y).pow(3)) // true |
|
x.comparedTo(y.modulo(z).negated() === x.cmp(y.mod(z).neg()) // true |
|
``` |
|
|
|
Most of the methods of JavaScript's `Number.prototype` and `Math` objects are replicated. |
|
|
|
```js |
|
x = new Decimal(255.5) |
|
x.toExponential(5) // '2.55500e+2' |
|
x.toFixed(5) // '255.50000' |
|
x.toPrecision(5) // '255.50' |
|
|
|
Decimal.sqrt('6.98372465832e+9823') // '8.3568682281821340204e+4911' |
|
Decimal.pow(2, 0.0979843) // '1.0702770511687781839' |
|
|
|
// Using `toFixed()` to avoid exponential notation: |
|
x = new Decimal('0.0000001') |
|
x.toString() // '1e-7' |
|
x.toFixed() // '0.0000001' |
|
``` |
|
|
|
And there are `isNaN` and `isFinite` methods, as `NaN` and `Infinity` are valid `Decimal` values. |
|
|
|
```js |
|
x = new Decimal(NaN) // 'NaN' |
|
y = new Decimal(Infinity) // 'Infinity' |
|
x.isNaN() && !y.isNaN() && !x.isFinite() && !y.isFinite() // true |
|
``` |
|
|
|
There is also a `toFraction` method with an optional *maximum denominator* argument. |
|
|
|
```js |
|
z = new Decimal(355) |
|
pi = z.dividedBy(113) // '3.1415929204' |
|
pi.toFraction() // [ '7853982301', '2500000000' ] |
|
pi.toFraction(1000) // [ '355', '113' ] |
|
``` |
|
|
|
All calculations are rounded according to the number of significant digits and rounding mode specified |
|
by the `precision` and `rounding` properties of the Decimal constructor. |
|
|
|
For advanced usage, multiple Decimal constructors can be created, each with their own independent |
|
configuration which applies to all Decimal numbers created from it. |
|
|
|
```js |
|
// Set the precision and rounding of the default Decimal constructor |
|
Decimal.set({ precision: 5, rounding: 4 }) |
|
|
|
// Create another Decimal constructor, optionally passing in a configuration object |
|
Dec = Decimal.clone({ precision: 9, rounding: 1 }) |
|
|
|
x = new Decimal(5) |
|
y = new Dec(5) |
|
|
|
x.div(3) // '1.6667' |
|
y.div(3) // '1.66666666' |
|
``` |
|
|
|
The value of a Decimal is stored in a floating point format in terms of its digits, exponent and sign, but these properties should be considered read-only. |
|
|
|
```js |
|
x = new Decimal(-12345.67); |
|
x.d // [ 12345, 6700000 ] digits (base 10000000) |
|
x.e // 4 exponent (base 10) |
|
x.s // -1 sign |
|
``` |
|
|
|
For further information see the [API](http://mikemcl.github.io/decimal.js/) reference in the *doc* directory. |
|
|
|
## Test |
|
|
|
To run the tests using Node.js from the root directory: |
|
|
|
```bash |
|
npm test |
|
``` |
|
|
|
Each separate test module can also be executed individually, for example: |
|
|
|
```bash |
|
node test/modules/toFraction |
|
``` |
|
|
|
To run the tests in a browser, open *test/test.html*. |
|
|
|
## Minify |
|
|
|
Two minification examples: |
|
|
|
Using [uglify-js](https://github.com/mishoo/UglifyJS) to minify the *decimal.js* file: |
|
|
|
```bash |
|
npm install uglify-js -g |
|
uglifyjs decimal.js --source-map url=decimal.min.js.map -c -m -o decimal.min.js |
|
``` |
|
|
|
Using [terser](https://github.com/terser/terser) to minify the ES module version, *decimal.mjs*: |
|
|
|
```bash |
|
npm install terser -g |
|
terser decimal.mjs --source-map url=decimal.min.mjs.map -c -m --toplevel -o decimal.min.mjs |
|
``` |
|
|
|
```js |
|
import Decimal from './decimal.min.mjs'; |
|
``` |
|
|
|
## Licence |
|
|
|
[The MIT Licence (Expat).](LICENCE.md)
|
|
|