alexbardas / bignumber.js

Arithmetic operations on big numbers

BigNumber.js

BigNumber.js is a light javascript library for node.js and the browser. It supports arithmetic operations on Big Integers.

It is build with performance in mind, uses the fastest algorithms and supports all basic arithmetic operations (+, -, *, /, %, ^, abs). Works with both positive and negative big integers.

: (http://alexbardas.github.io/bignumber.js/)

Install: npm install

Test: npm test

Usage:

• in node:

	var BigNumber = require('big-number');

    BigNumber(5).plus(97).minus(53).plus(434).multiply(5435423).add(321453).multiply(21).div(2).pow(2);
    // 760056543044267246001

• in the browser:

	<script src ="big-number.js"></script>

    n(5).plus(97).minus(53).plus(434).multiply(5435423).add(321453).multiply(21).div(2).pow(2);
    // 760056543044267246001

API

Supported methods: add/plus, minus/subtract, multiply/mult, divide/div, power/pow, mod, equals, lt, lte, gt, gte, isZero, abs

Addition

	BigNumber(2).plus(10); // or
	BigNumber(2).add(10);

Subtraction

	BigNumber(2).minus(10); // or
	BigNumber(2).subtract(10);

Multiplication

	BigNumber(2).multiply(10); // or
	BigNumber(2).mult(10);

Division

	BigNumber(2).divide(10); // or
	BigNumber(2).div(10);

Modulo

	BigNumber(53).mod(14);

Power

	BigNumber(2).power(10); // or
	BigNumber(2).pow(10);

bignumber.js's Issues

Not able to calculate negative pow greater than 20

I found that if the pow is -21, the library returns 0.

> BigNumber(10).pow( -20 ).toFixed()
"0.00000000000000000001"
> BigNumber(10).pow( -21 ).toFixed()
"0"

gt method

There seems to be a typo in the gt() method.
You wrote

return this._compare(n);

instead of

return this._compare(n) > 0;

How do we do modulus?

How do we do a%b?

Is it supported?

x.mod(BigNumber(1)) should be BigNumber(0) not 0

Expected:

const B = require('big-number');
B(4).mod(B(2)) // => B(0)
B(4).mod(B(1)) // => B(0)

Actual

const B = require('big-number');
B(4).mod(B(2)) // => B(0)
B(4).mod(B(1)) // => 0

This bug or special case makes mod very difficult to use generally. For example, this gcd algorithm is incorrect (crashes on some inputs, say gcd(2, 1)) because sometimes b will become a non-BigNumber and the equals call will fail:

function gcd(a, b) {
    while (! b.equals(0))
        [a, b] = [b, B(a).mod(b)];
    return a;
}

Typing big numbers.

How do we type big numbers?

Suppose I want to do the following.

BigNumber(7504438520191923456742887157841797954091357871698459738726187123489081745879172349)
    .plus(82357194235682371485692837452359245029452458945824812464614761874618746246);

Will that work? Or will those numbers lose precision as they get passed in? If it doesn't work, how would I type a large number?

BigNumber.power

BigNumber cannot pow 2 in really big number
91021647594683810219535933654934251479534157863306041279797813072970182896847013519788746925617742412580064669855271993332303862601121857197111304936174660068946112619451497811227831544662713616025713056142745265532924868545564456562967377707476694963292550067437071911620319036962646821706517883104319427589776171503427421006286620138994536026741907338715651076961517414781678466834080782790423347297765443660547911255471979643255640453462937683432589853084967564804569595290452514831259069315016939384258354788197112978494770163481690427679671395407675024855121278117722296863374565018760793372267398565546484659131594475885099741542528824006516878099438243730504595907621275173097558078678494502212310389559139551487470021354716990999521568289024733054261673747998101705483375896487726952293634912120275500036337311901682986775878946709944800823044033396510758699573091942394959689786213210578348474635262077425899441786725035553328026452422802571184526760818739053097052643982729237629409175523307125051123423491396102546815323588653936328628615602432518448303538232405804131604903499495861376245305892126969569043392980974614601204706253350233968292250887331060638846255969291434264133080795856852531165622202422443517686075515264924703983984245137815340118647487584962532702161707375834560416738870903709089460164561912334926064070232727897068371359156888369673941247625778500293901067192645551617214755766043215193444929085776138428151357166610151456660797273213324487581762214034910917260216051886976960536663942321221757622339195120334089625313271954034736335261275344693531607500848770372710727874045344249103808935116490810559994554396409524932616863896632449611640785363443241034414808494693466680894909818338793412170149875080188537007370517070292499658797864082748905569513683009815736353339735795214526008503314309369727400548897898035447336413801059990513929601975069120963700285348726450672792221862409261546394064650696898651450324279290182524898358142280625638393623893222302606104830421850041546493705828620006431426642535787077898579441444713493798807663631490012611935967739525658357718475398939690237812493186979555183835563140518721447026979765078376559664282348564388008216747311021473021887728991249288440548108234015928934121198428258476385596307956726794077335967586567648825464697565305444121395623938588154861760026258273428851652806836323449902435099389609943778037418050565391600159435195373848985262340521878307059674691690394981471621137706332978474872249104993321509438926410058468195857857333900359719773237369527433098886632111243176419242840887879373572960986442407617096730675524055633347746384347893079865362395984500942847998056857561817371966315779015848305902285346263893080017645397731496962460788877916069755819900627695397516936447294376763445560703837894256596911337684437930603449184224977131047887399462658540201534264524134026647556432874882337689861202969223007090595566029215032396590956865293289443544493708390728955860040741059833130180331043520845908486205910923641715752206315616969785216544787159528484073300081302189077581161855212239483320669733617326068219130531728249631339848772804856638009323213594311695320110481798655319999985671119360314997036564414864824899966257516356246471125985345793912683558163234139325551083299313158327582352835629901666186056929115813095652443122473352751694494192720924950043427965897395993899758259993593980408448899939188466703666236462956843331825476513445436759771653828602688161237012176266051792363018394007692559371619960543546023676051400072908551080565687955597534193929330427255324658331006277381079735142285475097368469865827591425279280401160706875893902153845941356745329810075393089875678911390539939594909652098424236102709308701962935978706943062605310646636581243598335182558344360950502730890095798169866419613095859508352751405211427124765614852753517856022104344940538432285263739599144419002222798902832507548645741854221071104490125583325707123619553142757573239427657573247370582600239368754911421475816074116685450515768385679499045603788720268342043797449572482110530350912912048224361354925406447876750716194861689893872062149728348416504299969131333437100145467935380084119501058654287923895140895110905741180396531004023412165461195292631149983849776545543123818020535216172956901650258991774122163366622813749703581606318821209045800739014306546784895744220392870321348009469481329401329818531111982013289934773992847788448168266197622925631236636943889675520187544251782103710626066503107504476090624779439803343834764096217085373874542730346439082298665258209427565297227406124327663846636726078600084421488387425640328418636833117139985791766948905632221637178998675941450199536707565541654779616325197208926405619875537302014470179249365016803871471317578985437358423148586225623633143909068301595232001953220330691366798341098224917162708627443538095424357425635067915946902748408154809033508259147188437185413081581200608968261523577171512714940134914703554883793504822816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

try yourself

Weird behavior on comparison

> let bn = require('big-number')
> let a = bn('5929390')
> let b = bn('852523')
> aa < bb
true

Super weird. The comparison is wrong.

Gives Wrong Number In 20 Digits

I tried to calculate this number:
304,153,525,784,175,760 * 82
and it gived me:
24,940,589,114,302,410,680
while the currect result is:
24,940,589,114,302,412,320
(the difference is in the last 4 digits).

_compare to 0 ?

Maybe I'm missing something, but the first line in _compare checks for (!n). This is causing an immediate false return if I try to compare anything to zero. It seems like it should be something like (typeof n === "undefined").

.equals(undefined) returns true

.equals(undefined) returns true. It should return false (or throw an exception).

var BigNumber = require('big-number');
var a = BigNumber(10);
console.log(a.equals(undefined) ? 't' : 'f'); // outputs 't'

var b = 10;
console.log(b == undefined ? 't' : 'f'); // outputs 'f'

How do we use this in a web browser?

How do we use this in a web browser?
Some documentation would be great.

BigNumber(0).mod(x) should be BigNumber(0) not 0

Expected:

const B = require('big-number');
B(0).mod(12) // => B(0)
B(16).mod(12) // => B(4)

Actual

const B = require('big-number');
B(0).mod(12) // => 0
B(16).mod(B(12)) // => B(4)

This makes it very difficult to use. For example the following code throws an exception because gt is not a function:

const B = require('big-number');
const a = B(0), b = B(a);
if (b.mod(12).gt(6)) {
   console.log(`${a} > ${b} x 12 + 6`);
} else {
   console.log(`${a} <= ${b} x 12 + 6`);
}

7601.11229246 invalid number

I cannot store bitcoin balance because bigNumber("7601.11229246") this is invalid number.

What is the workaround ? multiply ?

where

var test = 7601.11229246
console.log(test) //=> 7601.11229246