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caver.utils
caver-js utility APIs.
caver.utils provides utility functions.

caver.utils.randomHex(size)
The randomHex library to generate cryptographically strong pseudo-random HEX strings from a given byte size.
Parameters
Name
Type
Description
size
number
The byte size for the HEX string, e.g., 32 will result in a 32-byte HEX string with 64 characters prefixed with "0x".
Return Value
Type
Description
string
The generated random HEX string.
Example
> caver.utils.randomHex(32)
'0x861b56754dba7769f9740c3ad70b4694aa24d604c1dba3bac7ec45978927b8de'
> caver.utils.randomHex(4)
'0x5641d6ce'
> caver.utils.randomHex(2)
'0xf058'
> caver.utils.randomHex(1)
'0x7c'
> caver.utils.randomHex(0)
'0x'

caver.utils._()
The underscore library for many convenient JavaScript functions.
See the underscore API reference for details.
Example
> var _ = caver.utils._
> _.union([1,2],[3])
[1,2,3]
> _.each({my: 'object'}, function(value, key){ ... })
...

caver.utils.toBN(number)
Safely converts any given value (including BigNumber.js instances) into a BN.js instance, for handling big numbers in JavaScript.
Parameters
Name
Type
Description
number
string | number
number to convert to a big number.
Return Value
Type
Description
Object
The BN.js instance.
Examples
> caver.utils.toBN(1234).toString()
'1234'
> caver.utils.toBN('1234').add(caver.utils.toBN('1')).toString()
'1235'
> caver.utils.toBN('0xea').toString()
'234'

caver.utils.isBN(bn)
Checks if a given value is a BN.js instance.
Parameters
Name
Type
Description
bn
object
A BN.js instance.
Return Value
Type
Description
boolean
true if a given value is a BN.js instance.
Example
> var number = new caver.utils.BN(10)
> caver.utils.isBN(number)
true

caver.utils.isBigNumber(bignumber)
Checks if a given value is a BigNumber.js instance.
Parameters
Name
Type
Description
bignumber
object
A BigNumber.js instance.
Return Value
Type
Description
boolean
true if a given value is a BigNumber.js instance.
Example
> var number = new caver.utils.BigNumber(10)
> caver.utils.isBigNumber(number)
true

caver.utils.sha3(str)
caver.utils.keccak256(str) // ALIAS
Calculates the sha3 of the input.
NOTE: To mimic the sha3 behavior of Solidity use caver.utils.soliditySha3.
Parameters
Name
Type
Description
str
string
A string to hash.
Return Value
Type
Description
string
The result hash.
Example
> caver.utils.sha3('234') // taken as string
'0xc1912fee45d61c87cc5ea59dae311904cd86b84fee17cc96966216f811ce6a79'
> caver.utils.sha3(new caver.utils.BN('234')) // utils.sha3 stringify bignumber instance.
'0xc1912fee45d61c87cc5ea59dae311904cd86b84fee17cc96966216f811ce6a79'
> caver.utils.sha3(234)
null // can't calculate the has of a number
> caver.utils.sha3(0xea) // same as above, just the HEX representation of the number
null
> caver.utils.sha3('0xea') // will be converted to a byte array first, and then hashed
'0x2f20677459120677484f7104c76deb6846a2c071f9b3152c103bb12cd54d1a4a'

caver.utils.soliditySha3(param1 [, param2, ...])
Calculates the sha3 of given input parameters in the same way solidity would. This means arguments will be ABI converted and tightly packed before being hashed.
Parameters
Name
Type
Description
paramX
Mixed
Any type, or an object with {type: 'uint', value: '123456'} or {t: 'bytes', v: '0xfff456'}. Basic types are autodetected as follows: - string non numerical UTF-8 string is interpreted as string. - `string
Return Value
Type
Description
string
The result hash.
Example
> caver.utils.soliditySha3('234564535', '0xfff23243', true, -10)
// auto detects: uint256, bytes, bool, int256
'0x3e27a893dc40ef8a7f0841d96639de2f58a132be5ae466d40087a2cfa83b7179'
> caver.utils.soliditySha3('Hello!%') // auto detects: string
'0x661136a4267dba9ccdf6bfddb7c00e714de936674c4bdb065a531cf1cb15c7fc'
> caver.utils.soliditySha3('234') // auto detects: uint256
'0x61c831beab28d67d1bb40b5ae1a11e2757fa842f031a2d0bc94a7867bc5d26c2'
> caver.utils.soliditySha3(0xea) // same as above
'0x61c831beab28d67d1bb40b5ae1a11e2757fa842f031a2d0bc94a7867bc5d26c2'
> caver.utils.soliditySha3(new caver.utils.BN('234')) // same as above
'0x61c831beab28d67d1bb40b5ae1a11e2757fa842f031a2d0bc94a7867bc5d26c2'
> caver.utils.soliditySha3({type: 'uint256', value: '234'})) // same as above
'0x61c831beab28d67d1bb40b5ae1a11e2757fa842f031a2d0bc94a7867bc5d26c2'
> caver.utils.soliditySha3({t: 'uint', v: new caver.utils.BN('234')})) // same as above
'0x61c831beab28d67d1bb40b5ae1a11e2757fa842f031a2d0bc94a7867bc5d26c2'
> caver.utils.soliditySha3('0x407D73d8a49eeb85D32Cf465507dd71d507100c1')
'0x4e8ebbefa452077428f93c9520d3edd60594ff452a29ac7d2ccc11d47f3ab95b'
> caver.utils.soliditySha3({t: 'bytes', v: '0x407D73d8a49eeb85D32Cf465507dd71d507100c1'})
'0x4e8ebbefa452077428f93c9520d3edd60594ff452a29ac7d2ccc11d47f3ab95b' // same result as above
> caver.utils.soliditySha3({t: 'address', v: '0x407D73d8a49eeb85D32Cf465507dd71d507100c1'})
'0x4e8ebbefa452077428f93c9520d3edd60594ff452a29ac7d2ccc11d47f3ab95b' // same as above, but will do a checksum check, if its multi case
> caver.utils.soliditySha3({t: 'bytes32', v: '0x407D73d8a49eeb85D32Cf465507dd71d507100c1'})
'0x3c69a194aaf415ba5d6afca734660d0a3d45acdc05d54cd1ca89a8988e7625b4' // different result as above
> caver.utils.soliditySha3({t: 'string', v: 'Hello!%'}, {t: 'int8', v:-23}, {t: 'address', v: '0x85F43D8a49eeB85d32Cf465507DD71d507100C1d'})
'0xa13b31627c1ed7aaded5aecec71baf02fe123797fffd45e662eac8e06fbe4955'

caver.utils.isHex(hex)
Checks if a given string is a HEX string.
Parameters
Name
Type
Description
hex
string
The given HEX string.
Return Value
Type
Description
boolean
true if a given parameter is a HEX string.
Example
> caver.utils.isHex('0xc1912')
true
> caver.utils.isHex('c1912')
true
> caver.utils.isHex('0xZ1912')
false
> caver.utils.isHex('Hello')
false

caver.utils.isHexStrict(hex)
Checks if a given string is a HEX string. Difference to caver.utils.isHex is that it expects HEX to be prefixed with 0x.
Parameters
Name
Type
Description
hex
string
The given HEX string.
Return Value
Type
Description
boolean
true if a given string is a HEX string.
Example
> caver.utils.isHexStrict('0xc1912')
true
> caver.utils.isHexStrict('c1912')
false
> caver.utils.isHexStrict('0xZ1912')
false
> caver.utils.isHex('Hello')
false

caver.utils.isAddress(address)
Checks if a given string is a valid Klaytn address. It will also check the checksum if the address has upper and lowercase letters.
Parameters
Name
Type
Description
address
string
An address string.
Return Value
Type
Description
boolean
true if a given string is a valid Klaytn address.
Examples
> caver.utils.isAddress('0xc1912fee45d61c87cc5ea59dae31190fffff232d')
true
> caver.utils.isAddress('c1912fee45d61c87cc5ea59dae31190fffff232d')
true
> caver.utils.isAddress('0XC1912FEE45D61C87CC5EA59DAE31190FFFFF232D')
true // as all is uppercase, no checksum will be checked
> caver.utils.isAddress('0xc1912fEE45d61C87Cc5EA59DaE31190FFFFf232d')
true
> caver.utils.isAddress('0xC1912fEE45d61C87Cc5EA59DaE31190FFFFf232d')
false // wrong checksum

caver.utils.toChecksumAddress(address)
Converts an upper or lowercase Klaytn address to a checksum address.
Parameters
Name
Type
Description
address
string
An address string.
Return Value
Type
Description
string
The checksum address.
Examples
> caver.utils.toChecksumAddress('0xc1912fee45d61c87cc5ea59dae31190fffff232d')
'0xc1912fEE45d61C87Cc5EA59DaE31190FFFFf232d'
> caver.utils.toChecksumAddress('0XC1912FEE45D61C87CC5EA59DAE31190FFFFF232D')
'0xc1912fEE45d61C87Cc5EA59DaE31190FFFFf232d' // same as above

caver.utils.checkAddressChecksum(address)
Checks the checksum of a given address. Will also return false on non-checksum addresses.
Parameters
Name
Type
Description
address
string
An address string.
Return Value
Type
Description
boolean
true when the checksum of the address is valid, false if it is not a checksum address, or the checksum is invalid.
Examples
> caver.utils.checkAddressChecksum('0xc1912fEE45d61C87Cc5EA59DaE31190FFFFf232d')
true

caver.utils.toHex(mixed)
Converts any given value to HEX. The numeric strings will be interpreted as numbers. Text strings will be interpreted as UTF-8 strings.
Parameters
Name
Type
Description
mixed
string | number | BN | BigNumber
The input to convert to HEX.
Return Value
Type
Description
string
The resulting HEX string.
Examples
> caver.utils.toHex('234')
'0xea'
> caver.utils.toHex(234)
'0xea'
> caver.utils.toHex(new caver.utils.BN('234'))
'0xea'
> caver.utils.toHex(new caver.utils.BigNumber('234'))
'0xea'
> caver.utils.toHex('I have 100€')
'0x49206861766520313030e282ac'

caver.utils.hexToNumberString(hex)
Returns the number representation of a given HEX value as a string.
Parameters
Name
Type
Description
hexstring
string
A HEX string to be converted.
Return Value
Type
Description
string
The number as a string.
Examples
> caver.utils.hexToNumberString('0xea')
"234"

caver.utils.hexToNumber(hex)
Returns the number representation of a given HEX value.
NOTE: This is not useful for big numbers, rather use caver.utils.toBN.
Parameters
Name
Type
Description
hexstring
string
A HEX string to be converted.
Return Value
Type
Description
number
The number representation of a given HEX value.
Examples
> caver.utils.hexToNumber('0xea')
234

caver.utils.numberToHex(number)
Returns the HEX representation of a given number value.
Parameters
Name
Type
Description
number
string | number | BN | BigNumber
A number as string or number.
Return Value
Type
Description
string
The HEX value of the given number.
Examples
> caver.utils.numberToHex('234')
'0xea'

caver.utils.hexToUtf8(hex)
caver.utils.hexToString(hex) // ALIAS
Returns the UTF-8 string representation of a given HEX value.
Parameters
Name
Type
Description
hex
string
A HEX string to convert to a UTF-8 string.
Return Value
Type
Description
string
The UTF-8 string.
Examples
> caver.utils.hexToUtf8('0x49206861766520313030e282ac')
'I have 100€'

caver.utils.hexToAscii(hex)
Returns the ASCII string representation of a given HEX value.
Parameters
Name
Type
Description
hex
string
A HEX string to convert to an ASCII string.
Return Value
Type
Description
string
The ASCII string.
Examples
> caver.utils.hexToAscii('0x4920686176652031303021')
'I have 100!'

caver.utils.utf8ToHex(str)
caver.utils.stringToHex(str) // ALIAS
Returns the HEX representation of a given UTF-8 string.
Parameters
Name
Type
Description
str
string
A UTF-8 string to convert to a HEX string.
Return Value
Type
Description
string
The HEX string.
Examples
> caver.utils.utf8ToHex('I have 100€')
'0x49206861766520313030e282ac'

caver.utils.asciiToHex(str)
Returns the HEX representation of a given ASCII string.
Parameters
Name
Type
Description
str
string
An ASCII string to convert to a HEX string.
Return Value
Type
Description
string
The HEX string.
Examples
> caver.utils.asciiToHex('I have 100!')
'0x4920686176652031303021'

caver.utils.hexToBytes(hex)
Returns a byte array from the given HEX string.
Parameters
Name
Type
Description
hex
string
A HEX string to be converted.
Return Value
Type
Description
Array
The byte array.
Examples
> caver.utils.hexToBytes('0x000000ea')
[ 0, 0, 0, 234 ]

caver.utils.bytesToHex(byteArray)
Returns a HEX string from a byte array.
Parameters
Name
Type
Description
byteArray
Array
A byte array to convert.
Return Value
Type
Description
string
The HEX string.
Examples
> caver.utils.bytesToHex([ 72, 101, 108, 108, 111, 33, 36 ])
'0x48656c6c6f2124'

caver.utils.convertToPeb(number [, unit])
Converts any KLAY value into peb.
NOTE: "peb" is the smallest KLAY unit, and you should always use "peb" as the unit of KLAY. Convert to "KLAY" only for display reasons.
Parameters
Name
Type
Description
number
string | number | BN
The value.
unit
string
(optional, defaults to "KLAY") The unit of KLAY to convert from. number will be multiplied by one of the following multipliers for the unit provided: - peb: '1' - kpeb: '1000' - Mpeb: '1000000' - Gpeb: '1000000000' - Ston: '1000000000' - uKLAY: '1000000000000' - mKLAY: '1000000000000000' - KLAY: '1000000000000000000' - kKLAY: '1000000000000000000000' - MKLAY: '1000000000000000000000000' - GKLAY: '1000000000000000000000000000'
Return Value
Type
Description
string | BN
If the number parameter is an instance of BN, it returns a BN instance, otherwise a string.
Examples
> caver.utils.convertToPeb('1', 'KLAY')
'1000000000000000000'
> caver.utils.convertToPeb(caver.utils.toBN(1), 'KLAY')
<BN: de0b6b3a7640000>

caver.utils.convertFromPeb(number [, unit])
NOTE: "peb" is the smallest KLAY unit, and you should always use "peb" as the unit of KLAY. Convert to "KLAY" only for display reasons.
Parameters
Name
Type
Description
number
string | number | BN | BigNumber
The value in peb.
unit
string
(optional, defaults to "KLAY") The unit of KLAY to convert your "peb" into. number will be divided by one of the following denominators for the unit provided: - peb: '1' - kpeb: '1000' - Mpeb: '1000000' - Gpeb: '1000000000' - Ston: '1000000000' - uKLAY: '1000000000000' - mKLAY: '1000000000000000' - KLAY: '1000000000000000000' - kKLAY: '1000000000000000000000' - MKLAY: '1000000000000000000000000' - GKLAY: '1000000000000000000000000000'
Return Value
Type
Description
string
The string number.
Examples
> caver.utils.convertFromPeb('1', 'KLAY')
'0.000000000000000001'

caver.utils.unitMap
Shows all possible KLAY values and their amount in peb.
Return Value
Type
Description
Object
With the following properties: - peb: '1' - kpeb: '1000' - Mpeb: '1000000' - Gpeb: '1000000000' - Ston: '1000000000' - uKLAY: '1000000000000' - mKLAY: '1000000000000000' - KLAY: '1000000000000000000' - kKLAY: '1000000000000000000000' - MKLAY: '1000000000000000000000000' - GKLAY: '1000000000000000000000000000' - TKLAY: '1000000000000000000000000000000'
Examples
> caver.utils.unitMap
{
peb: '1',
kpeb: '1000',
Mpeb: '1000000',
Gpeb: '1000000000',
Ston: '1000000000',
uKLAY: '1000000000000',
mKLAY: '1000000000000000',
KLAY: '1000000000000000000',
kKLAY: '1000000000000000000000',
MKLAY: '1000000000000000000000000',
GKLAY: '1000000000000000000000000000',
TKLAY: '1000000000000000000000000000000'
}

caver.utils.klayUnit
Shows all KLAY units.
Return Value
Type
Description
Object
An object in which the units of KLAY used in Klaytn are defined. Each unit has its name and pebFactor. pebFactor is used when converting KLAY currently translated in each unit to 'peb'.
Examples
> caver.utils.klayUnit
{
peb: { unit: 'peb', pebFactor: 0 },
kpeb: { unit: 'kpeb', pebFactor: 3 },
Mpeb: { unit: 'Mpeb', pebFactor: 6 },
Gpeb: { unit: 'Gpeb', pebFactor: 9 },
ston: { unit: 'ston', pebFactor: 9 },
uKLAY: { unit: 'uKLAY', pebFactor: 12 },
mKLAY: { unit: 'mKLAY', pebFactor: 15 },
KLAY: { unit: 'KLAY', pebFactor: 18 },
kKLAY: { unit: 'kKLAY', pebFactor: 21 },
MKLAY: { unit: 'MKLAY', pebFactor: 24 },
GKLAY: { unit: 'GKLAY', pebFactor: 27 },
TKLAY: { unit: 'TKLAY', pebFactor: 30 }
}

caver.utils.padLeft(string, characterAmount [, sign])
caver.utils.leftPad(string, characterAmount [, sign]) // ALIAS
Adds padding on the left of a string. Useful for adding paddings to HEX strings.
Parameters
Name
Type
Description
string
string
The string to add padding on the left.
characterAmount
number
The number of characters the total string should have.
sign
string
(optional) The character sign to use, defaults to 0.
Return Value
Type
Description
string
The padded string.
Examples
> caver.utils.padLeft('0x3456ff', 20)
'0x000000000000003456ff'
> caver.utils.padLeft(0x3456ff, 20)
'0x000000000000003456ff'
> caver.utils.padLeft('Hello', 20, 'x')
'xxxxxxxxxxxxxxxHello'

caver.utils.padRight(str, characterAmount [, sign])
caver.utils.rightPad(str, characterAmount [, sign]) // ALIAS
Adds padding on the right of a string, Useful for adding paddings to HEX strings.
Parameters
Name
Type
Description
str
string
The string to add padding on the right.
characterAmount
number
The number of characters the total string should have.
sign
string
(optional) The character sign to use, defaults to 0.
Return Value
Type
Description
string
The padded string.
Examples
> caver.utils.padRight('0x3456ff', 20)
'0x3456ff00000000000000'
> caver.utils.padRight(0x3456ff, 20)
'0x3456ff00000000000000'
> caver.utils.padRight('Hello', 20, 'x')
'Helloxxxxxxxxxxxxxxx'

caver.utils.trimLeadingZero(hexString)
Removes leading zero from 0x-prefixed hex string.
Parameters
Name
Type
Description
hexString
string
A hex string to trim.
Return Value
Type
Description
string
A hex string without leading zero.
Examples
> caver.utils.trimLeadingZero('0x000011')
0x11

caver.utils.makeEven(hexString)
Returns a string to an even length.
Parameters
Name
Type
Description
hexString
string
A hex string to make even.
Return Value
Type
Description
string
A string with even length.
Examples
> caver.utils.makeEven('0x011')
0x0011

caver.utils.toTwosComplement(num)
Converts a negative number into a two's complement.
Parameters
Name
Type
Description
num
number | string | BigNumber
The number to convert.
Return Value
Type
Description
string
The converted hex string.
Examples
> caver.utils.toTwosComplement('-1')
'0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff'
> caver.utils.toTwosComplement(-1)
'0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff'
> caver.utils.toTwosComplement('0x1')
'0x0000000000000000000000000000000000000000000000000000000000000001'
> caver.utils.toTwosComplement(-15)
'0xfffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff1'
> caver.utils.toTwosComplement('-0x1')
'0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff'

caver.utils.isContractDeployment(transactionObject)
Returns true if the given transaction is a smart contract deploy transaction. It returns false if the transaction is not a smart contract deploy transaction. The result is determined by the values of the parameters in the transactionObject. Make sure all the mandatory parameters are set correctly.