javascript.builtins.Iterator - available since deno 1.37.0 #26298

ikeyan · 2025-03-26T09:43:12Z

What type of issue is this?

Incorrect support data (example: BrowserX says "86" but support was added in "40")

What information was incorrect, unhelpful, or incomplete?

Deno support for Iterator class and all of its methods

What browsers does this problem apply to, if applicable?

Deno

What did you expect to see?

The support for both of them was added in deno 1.37.0

Did you test this? If so, how?

Wrote a test iterator-tests.js:

import { strict as assert } from "node:assert";

function* gen() {
  yield 1;
  yield 2;
  yield 3;
}

Deno.test("Iterator", () => {
  assert.equal(typeof Iterator, "function");
});

Deno.test("Iterator[Symbol.iterator]", () => {
  assert.deepEqual(typeof Iterator.prototype[Symbol.iterator], "function");
});

Deno.test("Iterator constructor", () => {
  class MyIterator extends Iterator {
    next() {
      return { done: true, value: undefined };
    }
  }
  assert.deepEqual(new MyIterator().toArray(), []);
});

Deno.test("Iterator.drop", () => {
  assert.deepEqual(Array.from(gen().drop(1)), [2, 3]);
});

Deno.test("Iterator.every", () => {
  assert(gen().every((x) => x > 0));
  assert(!gen().every((x) => x > 1));
});

Deno.test("Iterator.filter", () => {
  assert.deepEqual(Array.from(gen().filter((x) => x % 2)), [1, 3]);
});

Deno.test("Iterator.find", () => {
  assert.deepEqual(
    gen().find((x) => x === 2),
    2,
  );
  assert.deepEqual(
    gen().find((x) => x === 4),
    undefined,
  );
});

Deno.test("Iterator.flatMap", () => {
  assert.deepEqual(Array.from(gen().flatMap((x) => [x, x])), [1, 1, 2, 2, 3, 3]);
});

Deno.test("Iterator.forEach", () => {
  let sum = 0;
  // biome-ignore lint/complexity/noForEach: This is a test
  gen().forEach((x) => {
    sum += x;
  });
  assert.deepEqual(sum, 6);
});

Deno.test("Iterator.from", () => {
  assert.deepEqual(Iterator.from(gen()).toArray(), [1, 2, 3]);
});

Deno.test("Iterator.map", () => {
  assert.deepEqual(Array.from(gen().map((x) => x * 2)), [2, 4, 6]);
});

Deno.test("Iterator.reduce", () => {
  const sum = gen().reduce((acc, x) => acc + x, 0);
  assert.deepEqual(sum, 6);
});

Deno.test("Iterator.some", () => {
  assert(gen().some((x) => x === 2));
  assert(!gen().some((x) => x === 4));
});

Deno.test("Iterator.take", () => {
  assert.deepEqual(Array.from(gen().take(2)), [1, 2]);
});

Deno.test("Iterator.toArray", () => {
  assert.deepEqual(gen().toArray(), [1, 2, 3]);
});

Run the test on deno 1.36.4 and deno 1.37.0 using asdf

% dvm install 1.37.0
% deno eval 'console.log(Deno.version)'
{ deno: "1.37.0", v8: "11.8.172.3", typescript: "5.2.2" }
% deno test iterator-tests.js
running 15 tests from ./iterator-tests.js
Iterator ... ok (0ms)
Iterator[Symbol.iterator] ... ok (0ms)
Iterator constructor ... ok (0ms)
Iterator.drop ... ok (0ms)
Iterator.every ... ok (0ms)
Iterator.filter ... ok (0ms)
Iterator.find ... ok (0ms)
Iterator.flatMap ... ok (0ms)
Iterator.forEach ... ok (0ms)
Iterator.from ... ok (0ms)
Iterator.map ... ok (0ms)
Iterator.reduce ... ok (0ms)
Iterator.some ... ok (0ms)
Iterator.take ... ok (0ms)
Iterator.toArray ... ok (0ms)

ok | 15 passed | 0 failed (34ms)

% dvm install 1.36.4
% deno eval 'console.log(Deno.version)'
{ deno: "1.36.4", v8: "11.6.189.12", typescript: "5.1.6" }
% deno test iterator-tests.js
running 15 tests from ./iterator-tests.js
Iterator ... FAILED (6ms)
Iterator[Symbol.iterator] ... FAILED (3ms)
Iterator constructor ... FAILED (3ms)
Iterator.drop ... FAILED (3ms)
Iterator.every ... FAILED (3ms)
Iterator.filter ... FAILED (3ms)
Iterator.find ... FAILED (3ms)
Iterator.flatMap ... FAILED (2ms)
Iterator.forEach ... FAILED (3ms)
Iterator.from ... FAILED (3ms)
Iterator.map ... FAILED (3ms)
Iterator.reduce ... FAILED (2ms)
Iterator.some ... FAILED (2ms)
Iterator.take ... FAILED (3ms)
Iterator.toArray ... FAILED (2ms)

 ERRORS

Iterator => ./iterator-tests.js:9:6
error: AssertionError: Values are not strictly equal:


    [Diff] Actual / Expected


-   undefined
+   function


    at new AssertionError (ext:deno_node/assertion_error.ts:414:11)
    at toNode (node:assert:44:15)
    at Function.strictEqual (node:assert:215:3)
    at file:///Users/me/iterator-tests.js:10:10

Iterator[Symbol.iterator] => ./iterator-tests.js:13:6
error: ReferenceError: Iterator is not defined
  assert.deepEqual(typeof Iterator.prototype[Symbol.iterator], "function");
                          ^
    at file:///Users/me/iterator-tests.js:14:27

Iterator constructor => ./iterator-tests.js:17:6
error: ReferenceError: Iterator is not defined
  class MyIterator extends Iterator {
                           ^
    at file:///Users/me/iterator-tests.js:18:28

Iterator.drop => ./iterator-tests.js:26:6
error: TypeError: gen(...).drop is not a function
  assert.deepEqual(Array.from(gen().drop(1)), [2, 3]);
                                    ^
    at file:///Users/me/iterator-tests.js:27:37

Iterator.every => ./iterator-tests.js:30:6
error: TypeError: gen(...).every is not a function
  assert(gen().every((x) => x > 0));
               ^
    at file:///Users/me/iterator-tests.js:31:16

Iterator.filter => ./iterator-tests.js:35:6
error: TypeError: gen(...).filter is not a function
  assert.deepEqual(Array.from(gen().filter((x) => x % 2)), [1, 3]);
                                    ^
    at file:///Users/me/iterator-tests.js:36:37

Iterator.find => ./iterator-tests.js:39:6
error: TypeError: gen(...).find is not a function
    gen().find((x) => x === 2),
          ^
    at file:///Users/me/iterator-tests.js:41:11

Iterator.flatMap => ./iterator-tests.js:50:6
error: TypeError: gen(...).flatMap is not a function
  assert.deepEqual(Array.from(gen().flatMap((x) => [x, x])), [1, 1, 2, 2, 3, 3]);
                                    ^
    at file:///Users/me/iterator-tests.js:51:37

Iterator.forEach => ./iterator-tests.js:54:6
error: TypeError: gen(...).forEach is not a function
  gen().forEach((x) => {
        ^
    at file:///Users/me/iterator-tests.js:57:9

Iterator.from => ./iterator-tests.js:63:6
error: ReferenceError: Iterator is not defined
  assert.deepEqual(Iterator.from(gen()).toArray(), [1, 2, 3]);
                   ^
    at file:///Users/me/iterator-tests.js:64:20

Iterator.map => ./iterator-tests.js:67:6
error: TypeError: gen(...).map is not a function
  assert.deepEqual(Array.from(gen().map((x) => x * 2)), [2, 4, 6]);
                                    ^
    at file:///Users/me/iterator-tests.js:68:37

Iterator.reduce => ./iterator-tests.js:71:6
error: TypeError: gen(...).reduce is not a function
  const sum = gen().reduce((acc, x) => acc + x, 0);
                    ^
    at file:///Users/me/iterator-tests.js:72:21

Iterator.some => ./iterator-tests.js:76:6
error: TypeError: gen(...).some is not a function
  assert(gen().some((x) => x === 2));
               ^
    at file:///Users/me/iterator-tests.js:77:16

Iterator.take => ./iterator-tests.js:81:6
error: TypeError: gen(...).take is not a function
  assert.deepEqual(Array.from(gen().take(2)), [1, 2]);
                                    ^
    at file:///Users/me/iterator-tests.js:82:37

Iterator.toArray => ./iterator-tests.js:85:6
error: TypeError: gen(...).toArray is not a function
  assert.deepEqual(gen().toArray(), [1, 2, 3]);
                         ^
    at file:///Users/me/iterator-tests.js:86:26

 FAILURES

Iterator => ./iterator-tests.js:9:6
Iterator[Symbol.iterator] => ./iterator-tests.js:13:6
Iterator constructor => ./iterator-tests.js:17:6
Iterator.drop => ./iterator-tests.js:26:6
Iterator.every => ./iterator-tests.js:30:6
Iterator.filter => ./iterator-tests.js:35:6
Iterator.find => ./iterator-tests.js:39:6
Iterator.flatMap => ./iterator-tests.js:50:6
Iterator.forEach => ./iterator-tests.js:54:6
Iterator.from => ./iterator-tests.js:63:6
Iterator.map => ./iterator-tests.js:67:6
Iterator.reduce => ./iterator-tests.js:71:6
Iterator.some => ./iterator-tests.js:76:6
Iterator.take => ./iterator-tests.js:81:6
Iterator.toArray => ./iterator-tests.js:85:6

FAILED | 0 passed | 15 failed (65ms)

error: Test failed

Can you link to any release notes, bugs, pull requests, or MDN pages related to this?

I read the release note but I could not find anything.

Do you have anything more you want to share?

No response

MDN URL

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Iterator

MDN metadata

MDN page report details

Query: javascript.builtins.Iterator
Report started: 2025-03-26T08:06:34.620Z

The text was updated successfully, but these errors were encountered:

caugner · 2025-03-26T15:54:26Z

I tried to verifying your findings locally with dvm, but for me the tests pass with 1.37.0, but not in 1.36.0.

% deno --version
deno 1.37.0 (release, aarch64-apple-darwin)
v8 11.8.172.3
typescript 5.2.2

This seems plausible, because iterator-helpers moved out of the --harmony flag in V8 11.8.160.

ikeyan · 2025-03-28T06:38:32Z

Confirmed all deno >= 1.37.0 from asdf except 1.38.0 has Iterator.
It looks like asdf-deno fooled me.
Updated the issue text.

caugner · 2025-03-31T08:42:14Z

Thanks for confirming, @ikeyan. Would you like to open a PR? 🙏

ikeyan · 2025-04-01T12:44:31Z

@caugner Here it is

ikeyan · 2025-04-01T16:19:36Z

Additional evidence

deno [1.38.1, 1.38.5] has Iterator

% dvm use 1.38.5
  Now using deno 1.38.5 in 1.05s
% deno eval 'console.log(Deno.version, Iterator)'
{ deno: "1.38.5", v8: "12.0.267.1", typescript: "5.2.2" } [Function: Iterator]
% dvm use 1.38.4
  Now using deno 1.38.4 in 1.06s
% deno eval 'console.log(Deno.version, Iterator)'
{ deno: "1.38.4", v8: "12.0.267.1", typescript: "5.2.2" } [Function: Iterator]
% dvm use 1.38.3
  Now using deno 1.38.3 in 1.07s
% deno eval 'console.log(Deno.version, Iterator)'
{ deno: "1.38.3", v8: "12.0.267.1", typescript: "5.2.2" } [Function: Iterator]
% dvm use 1.38.2
  Now using deno 1.38.2 in 1.07s
% deno eval 'console.log(Deno.version, Iterator)'
{ deno: "1.38.2", v8: "12.0.267.1", typescript: "5.2.2" } [Function: Iterator]
% dvm use 1.38.1
  Now using deno 1.38.1 in 1.06s
% deno eval 'console.log(Deno.version, Iterator)'
{ deno: "1.38.1", v8: "12.0.267.1", typescript: "5.2.2" } [Function: Iterator]

but deno 1.38.0 don't have Iterator

% dvm use 1.38.0
  Now using deno 1.38.0 in 1.03s
% deno eval 'console.log(Deno.version, Iterator)'
error: Uncaught ReferenceError: Iterator is not defined
console.log(Deno.version, Iterator)
                          ^
    at file:///Users/me/hobby/vggt/$deno$eval:1:27

ikeyan added the needs triage This issue needs to be confirmed label Mar 26, 2025

caugner added data:js Compat data for JS/ECMAScript features. https://developer.mozilla.org/docs/Web/JavaScript p3 Low priority – Community PRs encouraged. and removed needs triage This issue needs to be confirmed labels Mar 26, 2025

ikeyan changed the title ~~javascript.builtins.Iterator - available since deno 1.38.1~~ javascript.builtins.Iterator - available since deno 1.37.0 Mar 28, 2025

ikeyan linked a pull request Apr 1, 2025 that will close this issue

Deno 1.37.0 supports Iterator class and its methods #26370

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javascript.builtins.Iterator - available since deno 1.37.0 #26298

javascript.builtins.Iterator - available since deno 1.37.0 #26298

ikeyan commented Mar 26, 2025 •

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caugner commented Mar 26, 2025

ikeyan commented Mar 28, 2025 •

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caugner commented Mar 31, 2025

ikeyan commented Apr 1, 2025 •

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ikeyan commented Apr 1, 2025

javascript.builtins.Iterator - available since deno 1.37.0 #26298

javascript.builtins.Iterator - available since deno 1.37.0 #26298

Comments

ikeyan commented Mar 26, 2025 • edited Loading

What type of issue is this?

What information was incorrect, unhelpful, or incomplete?

What browsers does this problem apply to, if applicable?

What did you expect to see?

Did you test this? If so, how?

Can you link to any release notes, bugs, pull requests, or MDN pages related to this?

Do you have anything more you want to share?

MDN URL

MDN metadata

caugner commented Mar 26, 2025

ikeyan commented Mar 28, 2025 • edited Loading

caugner commented Mar 31, 2025

ikeyan commented Apr 1, 2025 • edited Loading

ikeyan commented Apr 1, 2025

ikeyan commented Mar 26, 2025 •

edited

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ikeyan commented Mar 28, 2025 •

edited

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ikeyan commented Apr 1, 2025 •

edited

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