WebAssembly traps surface in JavaScript as WebAssembly.RuntimeError, not as a normal Error

An out-of-bounds memory access, an integer division by zero, a failed indirect call signature check, or an executed unreachable instruction traps and unwinds into JavaScript as a WebAssembly.RuntimeError. The message names the trap kind, for instance memory access out of bounds or unreachable executed, and a catch block that only expects errors thrown by your own code will swallow it without distinguishing it from a logic bug.

A trap leaves the instance in a defined but usually unusable state: memory holds whatever it held, and C or Rust runtimes have typically abandoned an allocation midway, so the honest recovery is to discard the instance and create a new one rather than call in again. Rust panics compiled to wasm reach JavaScript the same way and lose their message unless a panic hook forwards it, which is what the console error panic hook crate exists to do.