BigDecimal for Javascript
BigDecimal for Javascript is a pure-Javascript implementation of immutable, arbitrary-precision, signed decimal numbers. BigDecimal supports decimal math with arbitrary precision.
For a limited time, we will throw in BigInteger support at no extra charge!
Purpose
If this is a problem for you:
node> 0.1 + 0.2
0.30000000000000004
Then you need BigDecimal for Javascript. BigDecimal is great for arithmetic of financial information, or anything exceeding the Javascript Number
(IEEE-754 float) type. Decimal did not make the cut in the new ECMAScript standards so it’s time we got our act together.
Usage
BigDecimal works in the browser and in Apache CouchDB. See the simple BigDecimal Couch app demo to compare server-side and client-side expression evaluation.
BigDecimal is available in the NPM repository for NodeJS.
npm install bigdecimal
Now use it normally. It is exactly like the Java 1.5 BigInteger
and BigDecimal
API. See the BigDecimal documentation for information.
var bigdecimal = require("bigdecimal");
var i = new bigdecimal.BigInteger("1234567890abcdefghijklmn", 24);
console.log("i is " + i);
var d = new bigdecimal.BigDecimal(i);
var x = new bigdecimal.BigDecimal("123456.123456789012345678901234567890");
console.log("d * x = " + d.multiply(x));
var two = new bigdecimal.BigDecimal('2');
console.log("Average = " + d.add(x).divide(two));
var down = bigdecimal.RoundingMode.DOWN();
console.log("d / x (25 decimal places) = " + d.divide(x, 25, DOWN));
There is also a command-line REPL tool for experimentation, bigdecimal.js
if you install with the -g
switch, or ./node_modules/.bin/bigdecimal.js
otherwise. The bigdecimal
module is already loaded, also available as BD
for convenience.
bigdecimal.js
BigDec> d = new BD.BigDecimal("123456.123456789012345678901234567890")
Implementation
This code is compiled Javascript, originating from the Google GWT project. GWT version 2.1 supports the Java BigDecimal class. The implementation came from the Apache Harmony project by way of gwt-java-math which optimized it for the Javascript compiler.
Compiled Javascript is a problem; however that is offset by these benefits:
- The implementation is mature, optimized, and maintained by Apache and Google
- The API is well-known, compatible with the J2SE
BigDecimal
and BigInteger
class
If you can’t stand the idea of running machine-generated code, please implement BigInteger
and BigDecimal
in native Javascript; convince the world your implementation is trustworthy, reasonably bug-free, and sure to be maintained for several years and I will glady include it in this project.
Builds
Ready-to-use Javascript builds are available in the tagged Git revisions. Click the Download Source
button at the top and choose a vX.Y
tag. The built code will be in lib/bigdecimal.js
.
To build BigDecimal yourself from source, follow these steps:
- Download the GWT SDK, version 2.4.0. Extract it in this checkout, as
gwt-2.4.0/
- Get Apache Ant if you don't have it (try just running
ant
at the command line). I just unpack it in this checkout and add $PWD/apche-ant-1.8.2/bin
to my PATH
. rake clean
rake
As with the prebuilt download, the CommonJS module will be in lib/bigdecimal.js
.
License
BigDecimal for Javascript is licensed under the Apache License, version 2.0.