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