big.js
A small, fast JavaScript library for arbitrary-precision decimal arithmetic.
The little sister to bignumber.js.
Features
- Faster, smaller and easier-to-use than JavaScript versions of Java's BigDecimal
- Only 2.6 KB minified and gzipped
- Simple API
- Replicates the
toExponential
, toFixed
and toPrecision
methods of JavaScript's Number type - Includes a
sqrt
method - Stores values in an accessible decimal floating point format
- No dependencies
- Comprehensive documentation and test set
Load
The library is the single JavaScript file big.js (or big.min.js, which is big.js minified).
It can be loaded via a script tag in an HTML document for the browser
<script src='./relative/path/to/big.js'></script>
or as a CommonJS, Node.js or AMD module using require
.
For Node, put the big.js file into the same directory as the file that is requiring it and use
var Big = require('./big');
or put it in a node_modules directory within the directory and use require('big')
.
To load with AMD loader libraries such as requireJS:
require(['big'], function(Big) {
// Use Big here in local scope. No global Big.
});
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: Big, the constructor of Big number instances.
It accepts a value of type Number, String or Big number Object.
x = new Big(123.4567)
y = Big('123456.7e-3') // 'new' is optional
z = new Big(x)
x.eq(y) && x.eq(z) && y.eq(z) // true
A Big number is immutable in the sense that it is not changed by its methods.
0.3 - 0.1 // 0.19999999999999998
x = new Big(0.3)
x.minus(0.1) // "0.2"
x // "0.3"
The methods that return a Big number can be chained.
x.div(y).plus(z).times(9).minus('1.234567801234567e+8').plus(976.54321).div('2598.11772')
x.sqrt().div(y).pow(3).gt(y.mod(z)) // true
Like JavaScript's Number type, there are toExponential
, toFixed
and toPrecision
methods.
x = new Big(255.5)
x.toExponential(5) // "2.55500e+2"
x.toFixed(5) // "255.50000"
x.toPrecision(5) // "255.50"
The maximum number of decimal places and the rounding mode used to round the results of the div
, sqrt
and pow
(with negative exponent) methods is determined by the value of the DP
and RM
properties of the Big
number constructor.
The other methods always give the exact result.
Big.DP = 10
Big.RM = 1
x = new Big(2);
y = new Big(3);
z = x.div(y) // "0.6666666667"
z.sqrt() // "0.8164965809"
z.pow(-3) // "3.3749999995"
z.times(z) // "0.44444444448888888889"
z.times(z).round(10) // "0.4444444445"
The value of a Big number is stored in a decimal floating point format in terms of a coefficient, exponent and sign.
x = new Big(-123.456);
x.c // "1,2,3,4,5,6" coefficient (i.e. significand)
x.e // 2 exponent
x.s // -1 sign
For futher information see the API reference in the doc folder.
Test
The test directory contains the test scripts for each Big number method.
The tests can be run with Node or a browser.
To test a single method, from a command-line shell at the test directory, use e.g.
$ node toFixed
To test all the methods
$ node every-test
For the browser, see single-test.html and every-test.html in the test/browser directory.
big-vs-number.html enables some of the methods of big.js to be compared with those of JavaScript's Number type.
Performance
The perf directory contains two applications and a lib directory containing the BigDecimal libraries used by both.
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.
(The GWT version doesn't work in IE 6.)
The BigDecimal in Node's npm registry is the GWT version. Despite its seeming popularity I have found it to have some serious bugs, see the Node script perf/lib/bigdecimal_GWT/bugs.js for examples of flaws in its remainder, divide and compareTo methods.
bigtime.js is a Node command-line application which tests the performance of big.js against the GWT version of
BigDecimal from the npm registry.
For example, to compare the time taken by the big.js plus
method and the BigDecimal add
method:
$ node bigtime plus 10000 40
This will time 10000 calls to each, using operands of up to 40 random digits and will check that the results match.
For help:
$ node bigtime -h
Build
I.e. minify.
For Node, if uglify-js is installed globally ( npm install uglify-js -g
) then
uglifyjs -o ./big.min.js ./big.js
will create big.min.js.
The big.min.js already present was created with Microsoft Ajax Minifier 4.95, as it produced a smaller file size.
Feedback
Feedback is welcome.
Bugs/comments/questions?
Open an issue, or email
Michael Mclaughlin
M8ch88l@gmail.com
Bitcoin donation to:
1DppGRQSjVSMgGxuygDEHQuWEdTiVEzJYG
Thank you
Licence
See LICENCE.
Change Log
####2.2.0
- 11/07/13 Added 'round up' mode.
####2.1.0
- 26/06/13 Allow e.g.
.1
and 2.
.
####2.0.0
- 12/05/13 Added
abs
method and replaced cmp
with eq
, gt
, gte
, lt
, and lte
methods.
####1.0.1
- Changed default value of MAX_DP to 1E6
####1.0.0
- 7/11/2012 Initial release