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<!DOCTYPE html>
<title>Custom Elements: [HTMLConstructor] derives prototype from NewTarget</title>
<meta name="author" title="Domenic Denicola" href="mailto:d@domenic.me">
<meta name="help" content="https://html.spec.whatwg.org/multipage/dom.html#htmlconstructor">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="../resources/custom-elements-helpers.js"></script>
<script>
"use strict";
test_with_window(w => {
let afterDefinition = false;
const proto1 = { "proto": "number one" };
const proto2 = { "proto": "number two" };
const TestElement = (function () {
assert_throws({ name: "prototype throws" }, () => {
const o = Reflect.construct(w.HTMLElement, [], new.target);
assert_equals(Object.getPrototypeOf(o), proto2,
"Must use the value returned from new.target.prototype");
assert_not_equals(Object.getPrototypeOf(o), proto1,
"Must not use the prototype stored at definition time");
});
}).bind({});
Object.defineProperty(TestElement, "prototype", {
get() {
return beforeDefinition ? proto1 : proto2;
}
});
w.customElements.define("test-element", TestElement);
beforeDefinition = true;
new TestElement();
}, "Use NewTarget's prototype, not the one stored at definition time");
test_with_window(w => {
// We have to not throw during define(), but throw during super()
let throws = false;
const TestElement = (function () {
assert_throws({ name: "prototype throws" }, () => {
return Reflect.construct(w.HTMLElement, [], new.target);
});
}).bind({});
Object.defineProperty(TestElement, "prototype", {
get() {
if (throws) {
throw { name: "prototype throws" };
}
return {};
}
});
w.customElements.define("test-element", TestElement);
throws = true;
new TestElement();
}, "Rethrow any exceptions thrown while getting the prototype");
test_with_window(w => {
for (const notAnObject of [null, undefined, 5, "string"]) {
// We have to return an object during define(), but not during super()
let returnNotAnObject = false;
const TestElement = (function () {
const o = Reflect.construct(w.HTMLElement, [], new.target);
assert_equals(Object.getPrototypeOf(o), window.HTMLElement,
"Must use the HTMLElement from the realm of NewTarget");
assert_not_equals(Object.getPrototypeOf(o), w.HTMLElement,
"Must not use the HTMLElement from the realm of the active function object (w.HTMLElement)");
return o;
}).bind({});
Object.defineProperty(TestElement, "prototype", {
get() {
return returnNotAnObject ? notAnObject : {};
}
});
w.customElements.define("test-element", TestElement);
returnNotAnObject = true;
new TestElement();
}
}, "If prototype is not object, derives the fallback from NewTarget's realm (autonomous custom elements)");
test_with_window(w => {
for (const notAnObject of [null, undefined, 5, "string"]) {
// We have to return an object during define(), but not during super()
let returnNotAnObject = false;
const TestElement = (function () {
const o = Reflect.construct(w.HTMLParagraphElement, [], new.target);
assert_equals(Object.getPrototypeOf(o), window.HTMLParagraphElement,
"Must use the HTMLParagraphElement from the realm of NewTarget");
assert_not_equals(Object.getPrototypeOf(o), w.HTMLParagraphElement,
"Must not use the HTMLParagraphElement from the realm of the active function object (w.HTMLParagraphElement)");
return o;
}).bind({});
Object.defineProperty(TestElement, "prototype", {
get() {
return returnNotAnObject ? notAnObject : {};
}
});
w.customElements.define("test-element", TestElement, { extends: "p" });
returnNotAnObject = true;
new TestElement();
}
}, "If prototype is not object, derives the fallback from NewTarget's realm (customized built-in elements)");
</script>
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