WebAssembly.Memory.prototype.buffer

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨October 2017⁩.

The read-only buffer prototype property of the WebAssembly.Memory object returns the buffer contained in the memory. Depending on whether or not the memory was constructed with shared: true, the buffer is either an ArrayBuffer or a SharedArrayBuffer.

Examples

Using buffer

The following example (see memory.html on GitHub, and view it live also) fetches and instantiates the loaded memory.wasm bytecode using the WebAssembly.instantiateStreaming() function, while importing the memory created in the line above. It then stores some values in that memory, exports a function, and uses the exported function to sum those values.

const memory = new WebAssembly.Memory({
  initial: 10,
  maximum: 100,
});

WebAssembly.instantiateStreaming(fetch("http://developer.mozilla.org/memory.wasm"), {
  js: { mem: memory },
}).then((obj) => {
  const summands = new DataView(memory.buffer);
  for (let i = 0; i < 10; i++) {
    summands.setUint32(i * 4, i, true); // WebAssembly is little endian
  }
  const sum = obj.instance.exports.accumulate(0, 10);
  console.log(sum);
});