Decimal

Simple decimal arithmetic for the browser and node.js!

Why?

Why don’t my numbers, like 0.1 + 0.2 add up to a nice round 0.3,
and instead I get a weird result like 0.30000000000000004?

Because internally, computers use a format (binary floating-point)
that cannot accurately represent a number like 0.1, 0.2 or 0.3 at all.

Source : http://floating-point-gui.de/

I wrote this because I needed to do simple computation in the browser and I couldn't find a lightweight library to do it.

How to use?

In the browser

<script src="lib/decimal.js"></script>

In node

npm install decimal

then in your program

var Decimal = require('decimal');

Examples

>>> 1.1 + 2.2;
3.3000000000000003

>>> Decimal('1.1').add('2.2').toNumber();
3.3

>>> 4.01 * 2.01;
8.060099999999998

>>> Decimal('4.01').mul('2.01').toNumber();
8.0601

>>> Decimal.mul('4.01', '2.01').toNumber();
8.0601

Order of Operations

Decimal.js orders operations from left-to-right. You should note that, building complex equations.

>>> 5+5*5
30

>>> Decimal('5').add('5').mul('5').toNumber()
50

Can I help?

Of course you can, I suck at math, and this implementation is very naive. If you are a math Guru and you see something wrong or a way to simplify things you can send in a pull request.

Methods

Decimal(n)

Create a new Decimal from n. n can be a string, integer, or another Decimal.

.toString()

Returns the Decimal instance as a string.

.toFixed()

Returns the Decimal instance as a string with fixed count of decimal part of number. Similar to Number.toFixed()

>>> 2.33333333333333.toFixed(20);
"2.33333333333332992865"

>>> Decimal('2.33333333333333').toFixed(20);
"2.33333333333333000000"

>>> 666666666666.0.toFixed(-2);
"666666666700"

>>> Decimal('666666666666.0').toFixed(-2);
"666666666600"

.toNumber()

Turn a Decimal into a Number.

.add(n)

Return a new Decimal containing the instance value plus n.

.sub(n)

Return a new Decimal containing the instance value minus n.

.mul(n)

Return a new Decimal containing the instance value multiplied by n.

.div(n)

Return a new Decimal containing the instance value integrally divided by n.

.abs(n)

Return a new Decimal containing the absolute value. Similar to Math.abs.

>>> Decimal('-600').abs();
"600"

>>> Decimal.abs('-600');
"600"

.floor(n)

Return a new Decimal containing the number rounded downward. Similar to Math.floor.

>>> Decimal('-1.5').floor().toString();
"-2"

>>> Decimal.floor('1.5').toString();
"1"

.ceil(n)

Return a new Decimal containing the number rounded upward. Similar to Math.ceil.

>>> Decimal('-1.5').ceil().toString();
"-1"

>>> Decimal.ceil('1.5').toString();
"2"