big.js

For client-side and server-side JS, we use big.js [1]. - We use strict mode [2] so we are forced to only input strings and never numbers. - We set rounding mode [3] to round-down. - Finally the default 20 decimal places [4] seems reliable enough for most of our use-cases. - It's also immutable and we can easily truncate decimal places with toFixed(dp) [5] [1] https://github.com/MikeMcl/big.js/ [2] http://mikemcl.github.io/big.js/#strict [3] http://mikemcl.github.io/big.js/#rm [4] http://mikemcl.github.io/big.js/#dp [5] http://mikemcl.github.io/big.js/#toF

My goto for any kind of arbitrary precision math in JavaScript is https://github.com/MikeMcl/big.js As others have noted, if you're doing any kind of math that involves floating point numbers and you will displaying them to a user, you'll almost certainly want something like this. While it's not specifically a "Money" class it can form an excellent base for one.

If you can find an atomic amount, (e.g. PicoDollars) I'd suggest using that. Javascript doesn't have an infinite precision integer type. In cases where that isn't possible, try an infinite precision javascript library. https://github.com/MikeMcl/big.js You could _probably_ find a way to shim big.js into OP's library :)