Qukit is an open source quantum circuit simulator implemented in rust and compiled for wasm. Qukit is capable of running 20+ q-bit simulations in browser or at the server (rust and node.js). You can use it in your javascript program to run quantum simulations.
In wasm you are limited to 2GB/4GB of memory, this means, with this library you are able to simulate up to 25 q-bits.
For a 25 q-bit system we need to keep track of 2^26 states.
A state is described by a complex value, which is composed of 2 f64 values, which equates to 2 x 8 = 16 Bytes.
This equates to a state vector of 2^26 x 16 = 1073731824 Bytes ≈ 1.07 GB.
For each transformation we need one source and one target vector, this leads to a memory usage of 2.14 GB.
With a future stabilisation of wasm64 we can simulate large vectors.