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LibJS: Implement Iterator.prototype.every

This commit is contained in:
Timothy Flynn 2023-06-25 20:08:29 -04:00 committed by Andreas Kling
parent 6ac1d5afae
commit 1f05b0638f
3 changed files with 162 additions and 0 deletions

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describe("errors", () => {
test("called with non-callable object", () => {
expect(() => {
Iterator.prototype.every(Symbol.hasInstance);
}).toThrowWithMessage(TypeError, "predicate is not a function");
});
test("iterator's next method throws", () => {
function TestError() {}
class TestIterator extends Iterator {
next() {
throw new TestError();
}
}
expect(() => {
new TestIterator().every(() => 0);
}).toThrow(TestError);
});
test("value returned by iterator's next method throws", () => {
function TestError() {}
class TestIterator extends Iterator {
next() {
return {
done: false,
get value() {
throw new TestError();
},
};
}
}
expect(() => {
new TestIterator().every(() => 0);
}).toThrow(TestError);
});
test("predicate function throws", () => {
function TestError() {}
class TestIterator extends Iterator {
next() {
return {
done: false,
value: 1,
};
}
}
expect(() => {
new TestIterator().every(() => {
throw new TestError();
});
}).toThrow(TestError);
});
});
describe("normal behavior", () => {
test("length is 1", () => {
expect(Iterator.prototype.every).toHaveLength(1);
});
test("predicate function can see every value", () => {
function* generator() {
yield "a";
yield "b";
}
let count = 0;
const result = generator().every((value, index) => {
++count;
switch (index) {
case 0:
expect(value).toBe("a");
break;
case 1:
expect(value).toBe("b");
break;
default:
expect().fail(`Unexpected reducer invocation: value=${value} index=${index}`);
break;
}
return true;
});
expect(count).toBe(2);
expect(result).toBeTrue();
});
test("iteration stops when predicate returns false", () => {
function* generator() {
yield "a";
yield "b";
yield "c";
}
let count = 0;
const result = generator().every(value => {
++count;
return value === "a";
});
expect(count).toBe(2);
expect(result).toBeFalse();
});
});