Having problem understanding how to deal with arbitrary precision

[StErMi]

Hi there,

I'm new to the library, but it seems the must-have library when dealing with currencies. I'm building a web app that deals with cryptocurrencies and their prices.

Each crypto has their own decimals and when I need to display the value of an amount of token X I need to multiply the amount for the value in dollars.

Now I'm having difficulties to understand how this should be handled via dinero.
For example:

• balance 4564660073892638156894 (this is the balance of the user with 18 decimals)
• balance formatted 4564.660073892638156894 (formatted balance using etherjs formatUtils formatUnits(BigNumber.from(balance), decimals)
• Token value in USD 0.223703 (each token is worth that value, 1 token === 1e18)
• Balance * Value 1021.1281525100048

How should I use dinero to correctly format this and then use it when I need to do math with different token prices to

[sarahdayan]

Hey @StErMi,

You can create Dinero objects in ETH, then convert them in USD with the convert function and format in with toFormat, like in this sandbox.

Note that I'm using native bigint to safely manipulate values, but for now the formatting part can give slight imprecisions (see #294).

If you want to use Ethers formatting utilities, you'll need to create a custom calculator using BigNumber from the library, so you can then make your own formatting utility by wrapping toSnapshot (until the issue linked above is fixed by #309).

For documentation on how to use a custom type and implement a calculator, please refer to the docs.