malloc.js

// get a pointer to 16 bytes of WASM memory
const byteLength = 16;
const pointer = Module._malloc(byteLength);

// e.g. let's set all values to 0xff (255)
for (let i = 0; i < byteLength; i++) {
  const idx = pointer + i;
  Module.HEAPU8[idx] = 0xff;
}

// when we are done with the pointer, make sure to release it
Module._free(pointer);