xhr/send-data-isolation.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>XMLHttpRequest send() data isolation</title>
<link rel="help" href="https://xhr.spec.whatwg.org/#the-send()-method">

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<script>
"use strict";

// These tests verify that `send()` on an XMLHttpRequest correctly copies its input data,
// so that subsequent modifications to the input do not affect what gets sent.

promise_test(async () => {
  const input = new Uint8Array([1, 2, 3, 4]);

  const xhr = new XMLHttpRequest();
  xhr.open("POST", "/xhr/resources/content.py", true);

  const loadPromise = new Promise((resolve, reject) => {
    xhr.onload = () => resolve(xhr);
    xhr.onerror = () => reject(new Error("XHR failed"));
  });

  xhr.send(input);
  input[0] = 99;

  const result = await loadPromise;
  const responseBytes = new Uint8Array(
    result.response.split("").map(c => c.charCodeAt(0))
  );
  assert_array_equals(
    responseBytes,
    [1, 2, 3, 4],
    "Sent data should not be affected by modifying the input Uint8Array"
  );
}, "Modifying a Uint8Array after send() does not affect the sent data");

promise_test(async () => {
  const input = new Uint8Array([5, 6, 7, 8]);
  const inputBuffer = input.buffer;

  const xhr = new XMLHttpRequest();
  xhr.open("POST", "/xhr/resources/content.py", true);

  const loadPromise = new Promise((resolve, reject) => {
    xhr.onload = () => resolve(xhr);
    xhr.onerror = () => reject(new Error("XHR failed"));
  });

  xhr.send(inputBuffer);
  input[0] = 99;

  const result = await loadPromise;
  const responseBytes = new Uint8Array(
    result.response.split("").map(c => c.charCodeAt(0))
  );
  assert_array_equals(
    responseBytes,
    [5, 6, 7, 8],
    "Sent data should not be affected by modifying the underlying ArrayBuffer"
  );
}, "Modifying an ArrayBuffer after send() does not affect the sent data");

promise_test(async () => {
  // Test with a view into a larger buffer (exercises offset handling)
  const largerBuffer = new ArrayBuffer(16);
  const view = new Uint8Array(largerBuffer, 4, 4);
  view.set([10, 11, 12, 13]);

  const xhr = new XMLHttpRequest();
  xhr.open("POST", "/xhr/resources/content.py", true);

  const loadPromise = new Promise((resolve, reject) => {
    xhr.onload = () => resolve(xhr);
    xhr.onerror = () => reject(new Error("XHR failed"));
  });

  xhr.send(view);
  view[0] = 99;

  const result = await loadPromise;
  const responseBytes = new Uint8Array(
    result.response.split("").map(c => c.charCodeAt(0))
  );
  assert_array_equals(
    responseBytes,
    [10, 11, 12, 13],
    "Sent data should not be affected by modifying a typed array view"
  );
}, "Modifying a typed array view after send() does not affect the sent data");
</script>