Rendering Without Copying

The naive version returns a Vec<u8> each frame, which allocates and copies the whole grid across the boundary sixty times a second.

Instead, expose a pointer:

#[wasm_bindgen]
impl Universe {
    pub fn cells(&self) -> *const Cell {
        self.cells.as_ptr()
    }
}

const cells = new Uint8Array(memory.buffer, universe.cells(), width * height);

JavaScript now reads wasm’s linear memory directly — zero copies.

One caveat that will bite you: if the Vec reallocates, wasm memory may grow and memory.buffer is detached. Re-create the Uint8Array after any operation that could resize.

Profile before optimizing further. In this project the render loop usually dominates the simulation, and people spend hours micro-tuning tick() for nothing.