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Test Info:
- This WPT test may be referenced by the following Test IDs:
- /html/webappapis/microtask-queuing/queue-microtask.window.html - WPT Dashboard Interop Dashboard
"use strict";
// This does not work as you expect because mutation observer compound microtasks are confusing.
// Basically you can only use it once per test.
function queueMicrotaskViaMO(cb) {
const observer = new MutationObserver(cb);
const node = document.createTextNode("");
observer.observe(node, { characterData: true });
node.data = "foo";
}
// Need to use promise_test to get sequential ordering; otherwise the global mutation observer
// compound microtask business screws us over.
promise_test(() => {
return new Promise(resolve => {
const happenings = [];
queueMicrotaskViaMO(() => happenings.push("x"));
queueMicrotask(() => happenings.push("a"));
queueMicrotask(() => {
assert_array_equals(happenings, ["x", "a"]);
resolve();
});
});
}, "It interleaves with MutationObservers as expected");
promise_test(() => {
return new Promise(resolve => {
const happenings = [];
queueMicrotask(() => happenings.push("a"));
Promise.reject().catch(() => happenings.push("x"));
queueMicrotaskViaMO(() => happenings.push(1));
Promise.resolve().then(() => happenings.push("y"));
queueMicrotask(() => happenings.push("b"));
queueMicrotask(() => happenings.push("c"));
queueMicrotask(() => {
assert_array_equals(happenings, ["a", "x", 1, "y", "b", "c"]);
resolve();
});
});
}, "It interleaves with MutationObservers and promises together as expected");