proposal-arraybuffer-equal

This is a proposal to add a new method, ArrayBuffer.isEqual(a: ArrayBuffer, b: ArrayBuffer), to JavaScript's ArrayBuffer class.

It has not yet been presented to the JavaScript standards committee.

Need discussion

Does it need to be extended to all TypedArray?
Not expected input type, throw TypeError or returns false?

The problem

const encoder = new TextEncoder();
const input = 'sample';
const a = encoder.encode(input);
const b = encoder.encode(input);
console.log(a === b); // returns false
console.log(a == b); // returns false

If the re-definition Abstract Equality Comparison or Strict Equality Comparison is break change behavior.

So we need to define a new method.

How compare two ArrayBuffer object is equality

To solve this problem, you need to define a method.

// The is TypeScript code
function isEqual(a: ArrayBuffer, b: ArrayBuffer) {
  if (!(a instanceof ArrayBuffer)) {
    return false;
  } else if (!(b instanceof ArrayBuffer)) {
    return false;
  } else if (a === b) {
    return true;
  } else if (a.byteLength !== b.byteLength) {
    return false;
  }
  const view1 = new DataView(a);
  const view2 = new DataView(b);
  for (let i = 0; i < view1.byteLength; i++) {
    if (view1.getUint8(i) !== view2.getUint8(i)) {
      return false;
    }
  }
  return true;
}

Polyfill

Wait for enter stage 1, then publish to npm registry.

# the is draft stage version (UNSTABLE)
npm install @nicelabs/proposal-arraybuffer-equals --registry https://npm.septs.me

`ArrayBuffer.isEqual`

To do this, we propose a new method, ArrayBuffer.isEqual(a, b), which compare two array buffer is equality (bit-wise)

// returns false
ArrayBuffer.isEqual(Uint8Array.of(0).buffer, undefined);
// returns false
ArrayBuffer.isEqual(Uint8Array.of(0).buffer, null);
// returns false
ArrayBuffer.isEqual(Uint8Array.of(0).buffer, Uint8Array.of(0, 1).buffer);
// returns true
ArrayBuffer.isEqual(Uint8Array.of(0).buffer, Uint8Array.of(0).buffer);
// returns true
ArrayBuffer.isEqual(
  Uint32Array.from([Number.MAX_SAFE_INTEGER]).buffer,
  Uint8Array.of(255, 255, 255, 255).buffer,
);

Related discussion

https://es.discourse.group/t/compare-two-arraybuffers-bit-wise-for-equality/413

License

JSCIG/proposal-arraybuffer-equal

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