How to convert BigNumber to bytes32?

[PaulRBerg]

In Solidity, doing this is as simple as:

function convert(uint256 n) returns (bytes32) {
    return bytes32(n);
}

How could we replicate this with ethers.js?

I found formatBytes32String in the docs but that is not quite the same thing as as I'm asking about here.

[zemse]

You can use hexZeroPad.

const amount = ethers.BigNumber.from(1);
ethers.utils.hexZeroPad(amount.toHexString(), 32) // 0x0000000000000000000000000000000000000000000000000000000000000001

And yeah parseBytes32String, formatBytes32String are different, use case for them is to store strings in smart contracts as bytes32 instead of the dynamic length type string. But that puts a limit of 32 utf8 characters, which can be reasonable for things like name and symbol (interestingly MKR uses bytes32 for name and symbol, as it was deployed before ERC20 was finalized)

[PaulRBerg]

This is awesome! Thanks for explaining.

[aster2709]

hi @PaulRBerg and @zemse found this discussion while searching my question.
what if we have to convert string to bytes32?

• in solidity bytes32("hello");
• in ethers?

[zemse]

You can use formatBytes32String

ethers-repl> formatBytes32String('hello')
'0x68656c6c6f000000000000000000000000000000000000000000000000000000'
ethers-repl> parseBytes32String('0x68656c6c6f000000000000000000000000000000000000000000000000000000')
'hello'

[aster2709]

this didn't work for this string "59587250f49f4e0d8b569efa3efdef2d"

> ethers.utils.formatBytes32String("59587250f49f4e0d8b569efa3efdef2d")
Uncaught Error: bytes32 string must be less than 32 bytes

looking for this output 0x3539353837323530663439663465306438623536396566613365666465663264 as from https://web3-type-converter.onbrn.com/
@zemse

[zemse]

formatBytes32String is an old method in ethers. It accepts only 31 length string.

To achieve what you'd want to do is: ethers.utils.hexZeroPad(ethers.utils.toUtf8Bytes('hello'), 32).

Also note that your string 59587250f49f4e0d8b569efa3efdef2d is hex value and hence it can be simply stored in a bytes16.

[aster2709]

works. thanks for the info