BigNumbers – Adding BigNumbers with ethers.js

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I am running tests and use ethers to format big numbers. I can't figure out how to add them.

For example, say I have two numbers I convert into 10 and 100 Finney:

      const x1 = utils.formatUnits("10000000000000000", "finney");
      const x2 = utils.formatUnits("100000000000000000", "finney");

If I console.log them, I see
console.log(x1) generates 10.0, while console.log(x2) generates 100.0. Interestingly,

const y = x2 - x1;

sets y to 90.0, while

const y = x2 + x1;

concatenates the strings, generating 100.010.0.

const y = x2 - - x1;

the above double negative correctly adds, generating 110.0! However, that's an ugly way to get what I want.

"x1.add(x2)", "utils.x1.add(x2)", etc., do not work. Can someone tell me how to add these numbers within my javascript file?

Best Answer

On ethers V5 the output is usually a object with two fields, isBignumber (boolean) and _hex field with a string representing the hexadecimal value of that number. So you need to pass inside Number(bigNumber._hex) in orther to make math. Ethers V6 would returning straight a BigInt(), big integers can do math with eachother but if you try to perform math between a big integer and a regular number it will also complain. Again you need to pass it inside Number().

Related Solutions

[Ethereum] Ethers js adding provider

**** EDIT ****

Figured it out.

ethers.Wallet.fromEncryptedJson(encryptedWallet, passphrase).then((myWallet) => {
    const loggedInWallet = myWallet.connect(provider);
    // loggedInWallet will now have provider added
}

Currently the only solve I have been able to get to work is kinda hacky. Object assign does not seem to copy all the key pairs for some reason. I used Object.create and passed in the wallet once un-encrypted.

const LoggedInWallet = Object.create(walletFromUnencryption);
LoggedInWallet.__proto__ = myWallet.__proto__;
LoggedInWallet._ethersType = myWallet._ethersType;
LoggedInWallet.provider = provider;
LoggedInWallet.signingKey = myWallet.signingKey;

This gave me a wallet with the needed data for use while user is logged in.

Not ideal it would seem. I would think when un-encrypting the wallet you could do something like:

ethers.Wallet.fromEncryptedJson(encryptedWallet, passphrase, provider).then((walletFromUnencryption) =>

adding provider as an option passing in, but doesnt seem like thats possible. So I will resort to what I have working for now till I can find the solution how to get the provider when un-encrypting the wallet

Ethers.js – How Does Comparing BigNumbers with Ethers Work?

I exactly ran into the same problem. You should use the built.in methods in bignumber:

let a = ethers.BigNumber.from('30');
let b = ethers.BigNumber.from('120');
 a.lt(b) // returns true  as 30 is lower than (lt) 120

Here you use lt (lower than), you can use:

eq: equal
gte: greater or equal
gt: greater
lte: lower or equal
lt: lower

Hope it helps

Best Answer

Related Solutions

[Ethereum] Ethers js adding provider

Ethers.js – How Does Comparing BigNumbers with Ethers Work?

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