index.js

const wasm = require('webassembly')
const assert = require('assert')

wasm.load('crc32.wasm').then(main).catch(e => console.error(e))

// wrapper
const _crc32 = ({crc32, _malloc, _free}, memory) => (buf, crc = 0) => {
  if (!Buffer.isBuffer(buf)) {
    buf = Buffer.from(buf)
  }
  
  // allocate internal memory for Buffer buf
  // return pointer (int value) to free memory
  const mem = _malloc(buf.length)
  
  // fill memory, copy data
  memory.U8.set(buf, mem)
  
  // call wasm function directly
  const result = crc32(mem, buf.length, crc)
  
  // free memory
  _free(mem)
  return result
}

function main({exports, memory}) {
  const crc32 = _crc32(exports, memory)
  const crc = crc32('123456789') >>> 0
  
  assert.strictEqual(crc, 0xcbf43926)
  console.log(`crc32('123456789') =`, crc)
}