bignumber.js VS safe-decimal

If you use floating-points for currency (instead of whole-numbers like you probably should) libraries like bignumber.js help keep your code away from the binary floating-point pitfalls of IEEE-754 which manifests in the standard JavaScript number type:

This issue (well, another one in a widely used JS library) is what brought me to dig deeper into these "arbitrary precision" libraries and understand why this happens. I thought they were using rational numbers, but that's not the case. And this is what led me to think about how to solve this problem.

ERC20 has decimals fields and must be handled with digit awareness. I wanted to use only one library, but I used both ether.js's BigNumber and bignumber.js (for display purpose).

Most programming languages ( JavaScript, PHP, Go, Python, Java, C# ) have built-in support or 3rd-party libraries for handling this data type, even though the internal implementations can differ:

I'm working on a project where users will enter numbers like 9,999,999,999.99999 (up to 15 digits, up to 5 of them decimal) and we are having a problem with Numbers losing precision beyond certain number of digits (a typical issue for IEEE Standard 754 Floating Point Numbers, the 0.1 + 0.2 problem). I've solved this problem in a few projects before with the help of decimal.js or bignumber,js . In those cases, we kept user-input as strings and used a few custom-made numeric textbox widgets to accommodate this. Unfortunately, those widgets were proprietary... Now I need one again, but can't find anything. Do they exist?

Either avoid floating-point, perhaps using BigInt, or use a library like BigNumber.js. (Incidentally, I wrote an eslint plugin to enforce its use.)

To solve the problem while JavaScript waits on its own BigDecimal API, you can use something like bignumber.js to perform your calculations.

You need to use something like BigNumber.js

I've published this article with what I've learned, and did a Rust implementation on this repo https://github.com/voliva/safe-decimal

I've implemented this in Rust, and a Typescript implementation is on the way. You can find the repo here. I've called it SafeDecimal. I won't go in detail on the implementation, but let's compare it with the other usual approaches.