From 534683640d13aa5c7add05cadcaccdca34c7a3ff Mon Sep 17 00:00:00 2001
From: tsctx <91457664+tsctx@users.noreply.github.com>
Date: Mon, 12 Feb 2024 21:33:04 +0900
Subject: [PATCH 01/13] perf: always use the same prototype Iterator

---
 lib/fetch/formdata.js | 27 +++++++------------------
 lib/fetch/headers.js  | 28 ++++++++------------------
 lib/fetch/util.js     | 46 ++++++++++++++++++++++++++++---------------
 3 files changed, 45 insertions(+), 56 deletions(-)

diff --git a/lib/fetch/formdata.js b/lib/fetch/formdata.js
index add64aa9226..5eb7c17c93a 100644
--- a/lib/fetch/formdata.js
+++ b/lib/fetch/formdata.js
@@ -1,6 +1,6 @@
 'use strict'
 
-const { isBlobLike, makeIterator } = require('./util')
+const { isBlobLike, createIterator } = require('./util')
 const { kState } = require('./symbols')
 const { kEnumerableProperty } = require('../core/util')
 const { File: UndiciFile, FileLike, isFileLike } = require('./file')
@@ -10,6 +10,8 @@ const { File: NativeFile } = require('node:buffer')
 /** @type {globalThis['File']} */
 const File = NativeFile ?? UndiciFile
 
+const makeIterator = createIterator('FormData', kState, 'name', 'value')
+
 // https://xhr.spec.whatwg.org/#formdata
 class FormData {
   constructor (form) {
@@ -158,34 +160,19 @@ class FormData {
   entries () {
     webidl.brandCheck(this, FormData)
 
-    return makeIterator(
-      () => this[kState],
-      'FormData',
-      'key+value',
-      'name', 'value'
-    )
+    return makeIterator(this, 'key+value')
   }
 
   keys () {
     webidl.brandCheck(this, FormData)
 
-    return makeIterator(
-      () => this[kState],
-      'FormData',
-      'key',
-      'name', 'value'
-    )
+    return makeIterator(this, 'key')
   }
 
   values () {
     webidl.brandCheck(this, FormData)
 
-    return makeIterator(
-      () => this[kState],
-      'FormData',
-      'value',
-      'name', 'value'
-    )
+    return makeIterator(this, 'value')
   }
 
   /**
@@ -203,7 +190,7 @@ class FormData {
       )
     }
 
-    for (const [key, value] of this) {
+    for (const [key, value] of makeIterator(this, 'key+value')) {
       callbackFn.call(thisArg, value, key, this)
     }
   }
diff --git a/lib/fetch/headers.js b/lib/fetch/headers.js
index 504942edc6e..9a0a1e07ac8 100644
--- a/lib/fetch/headers.js
+++ b/lib/fetch/headers.js
@@ -1,4 +1,5 @@
 // https://github.com/Ethan-Arrowood/undici-fetch
+// https://github.com/Ethan-Arrowood/undici-fetch
 
 'use strict'
 
@@ -6,7 +7,7 @@ const { kHeadersList, kConstruct } = require('../core/symbols')
 const { kGuard } = require('./symbols')
 const { kEnumerableProperty } = require('../core/util')
 const {
-  makeIterator,
+  createIterator,
   isValidHeaderName,
   isValidHeaderValue
 } = require('./util')
@@ -16,6 +17,8 @@ const assert = require('node:assert')
 const kHeadersMap = Symbol('headers map')
 const kHeadersSortedMap = Symbol('headers map sorted')
 
+const makeIterator = createIterator('Headers', kHeadersSortedMap, 0, 1)
+
 /**
  * @param {number} code
  */
@@ -507,34 +510,19 @@ class Headers {
   keys () {
     webidl.brandCheck(this, Headers)
 
-    return makeIterator(
-      () => this[kHeadersSortedMap],
-      'Headers',
-      'key',
-      0, 1
-    )
+    return makeIterator(this, 'key')
   }
 
   values () {
     webidl.brandCheck(this, Headers)
 
-    return makeIterator(
-      () => this[kHeadersSortedMap],
-      'Headers',
-      'value',
-      0, 1
-    )
+    return makeIterator(this, 'value')
   }
 
   entries () {
     webidl.brandCheck(this, Headers)
 
-    return makeIterator(
-      () => this[kHeadersSortedMap],
-      'Headers',
-      'key+value',
-      0, 1
-    )
+    return makeIterator(this, 'key+value')
   }
 
   /**
@@ -552,7 +540,7 @@ class Headers {
       )
     }
 
-    for (const [key, value] of this) {
+    for (const [key, value] of makeIterator(this, 'key+value')) {
       callbackFn.call(thisArg, value, key, this)
     }
   }
diff --git a/lib/fetch/util.js b/lib/fetch/util.js
index c5a6b46b170..a3c98a3b809 100644
--- a/lib/fetch/util.js
+++ b/lib/fetch/util.js
@@ -739,18 +739,14 @@ const esIteratorPrototype = Object.getPrototypeOf(Object.getPrototypeOf([][Symbo
 
 /**
  * @see https://webidl.spec.whatwg.org/#dfn-iterator-prototype-object
- * @param {() => unknown} iterator
  * @param {string} name name of the instance
- * @param {'key'|'value'|'key+value'} kind
+ * @param {symbol} kInternalIterator
  * @param {string | number} [keyIndex]
  * @param {string | number} [valueIndex]
  */
-function makeIterator (iterator, name, kind, keyIndex = 0, valueIndex = 1) {
-  const object = {
-    index: 0,
-    kind,
-    target: iterator
-  }
+function createIterator (name, kInternalIterator, keyIndex = 0, valueIndex = 1) {
+  const kInternalObject = Symbol('internal Object')
+
   // The [[Prototype]] internal slot of an iterator prototype object must be %IteratorPrototype%.
   const iteratorObject = Object.create(esIteratorPrototype)
 
@@ -767,17 +763,18 @@ function makeIterator (iterator, name, kind, keyIndex = 0, valueIndex = 1) {
 
       // 5. If object is not a default iterator object for interface,
       //    then throw a TypeError.
-      if (Object.getPrototypeOf(this) !== iteratorObject) {
+      if (typeof this !== 'object' || this === null || !(kInternalObject in this)) {
         throw new TypeError(
           `'next' called on an object that does not implement interface ${name} Iterator.`
         )
       }
+      const state = this[kInternalObject]
 
       // 6. Let index be object’s index.
       // 7. Let kind be object’s kind.
       // 8. Let values be object’s target's value pairs to iterate over.
-      const { index, kind, target } = object
-      const values = target()
+      const { index, kind, target } = state
+      const values = target[kInternalIterator]
 
       // 9. Let len be the length of values.
       const len = values.length
@@ -790,7 +787,7 @@ function makeIterator (iterator, name, kind, keyIndex = 0, valueIndex = 1) {
       // 11. Let pair be the entry in values at index index.
       const { [keyIndex]: key, [valueIndex]: value } = values[index]
       // 12. Set object’s index to index + 1.
-      object.index = index + 1
+      state.index = index + 1
       // 13. Return the iterator result for pair and kind.
       // https://webidl.spec.whatwg.org/#iterator-result
       // 1. Let result be a value determined by the value of kind:
@@ -844,9 +841,26 @@ function makeIterator (iterator, name, kind, keyIndex = 0, valueIndex = 1) {
     configurable: true
   })
 
-  // esIteratorPrototype needs to be the prototype of iteratorObject
-  // which is the prototype of an empty object. Yes, it's confusing.
-  return Object.create(iteratorObject)
+  /**
+   * @param {unknown} target
+   * @param {'key'|'value'|'key+value'} kind
+   */
+  return function (target, kind) {
+    // esIteratorPrototype needs to be the prototype of iteratorObject
+    // which is the prototype of an empty object. Yes, it's confusing.
+    const iterator = Object.create(iteratorObject)
+    Object.defineProperty(iterator, kInternalObject, {
+      value: {
+        target,
+        kind,
+        index: 0
+      },
+      writable: false,
+      enumerable: false,
+      configurable: true
+    })
+    return iterator
+  }
 }
 
 /**
@@ -1365,7 +1379,7 @@ module.exports = {
   sameOrigin,
   normalizeMethod,
   serializeJavascriptValueToJSONString,
-  makeIterator,
+  createIterator,
   isValidHeaderName,
   isValidHeaderValue,
   isErrorLike,

From 8a2300a1eba67fccda73e5e79c972d7f4943bab2 Mon Sep 17 00:00:00 2001
From: tsctx <91457664+tsctx@users.noreply.github.com>
Date: Tue, 13 Feb 2024 02:24:27 +0900
Subject: [PATCH 02/13] add iteratorMixin

---
 lib/fetch/formdata.js | 52 ++++--------------------------
 lib/fetch/headers.js  | 52 ++++--------------------------
 lib/fetch/util.js     | 74 +++++++++++++++++++++++++++++++++++++++++--
 lib/fetch/webidl.js   |  2 +-
 4 files changed, 85 insertions(+), 95 deletions(-)

diff --git a/lib/fetch/formdata.js b/lib/fetch/formdata.js
index 5eb7c17c93a..e0a5cf6c199 100644
--- a/lib/fetch/formdata.js
+++ b/lib/fetch/formdata.js
@@ -1,6 +1,6 @@
 'use strict'
 
-const { isBlobLike, createIterator } = require('./util')
+const { isBlobLike, iteratorMixin } = require('./util')
 const { kState } = require('./symbols')
 const { kEnumerableProperty } = require('../core/util')
 const { File: UndiciFile, FileLike, isFileLike } = require('./file')
@@ -10,8 +10,6 @@ const { File: NativeFile } = require('node:buffer')
 /** @type {globalThis['File']} */
 const File = NativeFile ?? UndiciFile
 
-const makeIterator = createIterator('FormData', kState, 'name', 'value')
-
 // https://xhr.spec.whatwg.org/#formdata
 class FormData {
   constructor (form) {
@@ -156,47 +154,9 @@ class FormData {
       this[kState].push(entry)
     }
   }
-
-  entries () {
-    webidl.brandCheck(this, FormData)
-
-    return makeIterator(this, 'key+value')
-  }
-
-  keys () {
-    webidl.brandCheck(this, FormData)
-
-    return makeIterator(this, 'key')
-  }
-
-  values () {
-    webidl.brandCheck(this, FormData)
-
-    return makeIterator(this, 'value')
-  }
-
-  /**
-   * @param {(value: string, key: string, self: FormData) => void} callbackFn
-   * @param {unknown} thisArg
-   */
-  forEach (callbackFn, thisArg = globalThis) {
-    webidl.brandCheck(this, FormData)
-
-    webidl.argumentLengthCheck(arguments, 1, { header: 'FormData.forEach' })
-
-    if (typeof callbackFn !== 'function') {
-      throw new TypeError(
-        "Failed to execute 'forEach' on 'FormData': parameter 1 is not of type 'Function'."
-      )
-    }
-
-    for (const [key, value] of makeIterator(this, 'key+value')) {
-      callbackFn.call(thisArg, value, key, this)
-    }
-  }
 }
 
-FormData.prototype[Symbol.iterator] = FormData.prototype.entries
+iteratorMixin('FormData', FormData, kState, 'name', 'value')
 
 Object.defineProperties(FormData.prototype, {
   append: kEnumerableProperty,
@@ -205,11 +165,11 @@ Object.defineProperties(FormData.prototype, {
   getAll: kEnumerableProperty,
   has: kEnumerableProperty,
   set: kEnumerableProperty,
-  entries: kEnumerableProperty,
-  keys: kEnumerableProperty,
-  values: kEnumerableProperty,
+  // entries: kEnumerableProperty,
+  // keys: kEnumerableProperty,
+  // values: kEnumerableProperty,
   forEach: kEnumerableProperty,
-  [Symbol.iterator]: { enumerable: false },
+  // [Symbol.iterator]: { enumerable: false },
   [Symbol.toStringTag]: {
     value: 'FormData',
     configurable: true
diff --git a/lib/fetch/headers.js b/lib/fetch/headers.js
index 9a0a1e07ac8..00a14269f05 100644
--- a/lib/fetch/headers.js
+++ b/lib/fetch/headers.js
@@ -7,7 +7,7 @@ const { kHeadersList, kConstruct } = require('../core/symbols')
 const { kGuard } = require('./symbols')
 const { kEnumerableProperty } = require('../core/util')
 const {
-  createIterator,
+  iteratorMixin,
   isValidHeaderName,
   isValidHeaderValue
 } = require('./util')
@@ -17,8 +17,6 @@ const assert = require('node:assert')
 const kHeadersMap = Symbol('headers map')
 const kHeadersSortedMap = Symbol('headers map sorted')
 
-const makeIterator = createIterator('Headers', kHeadersSortedMap, 0, 1)
-
 /**
  * @param {number} code
  */
@@ -507,44 +505,6 @@ class Headers {
     return headers
   }
 
-  keys () {
-    webidl.brandCheck(this, Headers)
-
-    return makeIterator(this, 'key')
-  }
-
-  values () {
-    webidl.brandCheck(this, Headers)
-
-    return makeIterator(this, 'value')
-  }
-
-  entries () {
-    webidl.brandCheck(this, Headers)
-
-    return makeIterator(this, 'key+value')
-  }
-
-  /**
-   * @param {(value: string, key: string, self: Headers) => void} callbackFn
-   * @param {unknown} thisArg
-   */
-  forEach (callbackFn, thisArg = globalThis) {
-    webidl.brandCheck(this, Headers)
-
-    webidl.argumentLengthCheck(arguments, 1, { header: 'Headers.forEach' })
-
-    if (typeof callbackFn !== 'function') {
-      throw new TypeError(
-        "Failed to execute 'forEach' on 'Headers': parameter 1 is not of type 'Function'."
-      )
-    }
-
-    for (const [key, value] of makeIterator(this, 'key+value')) {
-      callbackFn.call(thisArg, value, key, this)
-    }
-  }
-
   [Symbol.for('nodejs.util.inspect.custom')] () {
     webidl.brandCheck(this, Headers)
 
@@ -552,7 +512,7 @@ class Headers {
   }
 }
 
-Headers.prototype[Symbol.iterator] = Headers.prototype.entries
+iteratorMixin('Headers', Headers, kHeadersSortedMap, 0, 1)
 
 Object.defineProperties(Headers.prototype, {
   append: kEnumerableProperty,
@@ -561,11 +521,11 @@ Object.defineProperties(Headers.prototype, {
   has: kEnumerableProperty,
   set: kEnumerableProperty,
   getSetCookie: kEnumerableProperty,
-  keys: kEnumerableProperty,
-  values: kEnumerableProperty,
-  entries: kEnumerableProperty,
+  // keys: kEnumerableProperty,
+  // values: kEnumerableProperty,
+  // entries: kEnumerableProperty,
   forEach: kEnumerableProperty,
-  [Symbol.iterator]: { enumerable: false },
+  // [Symbol.iterator]: { enumerable: false },
   [Symbol.toStringTag]: {
     value: 'Headers',
     configurable: true
diff --git a/lib/fetch/util.js b/lib/fetch/util.js
index a3c98a3b809..0737d874c09 100644
--- a/lib/fetch/util.js
+++ b/lib/fetch/util.js
@@ -6,9 +6,10 @@ const { redirectStatusSet, referrerPolicySet: referrerPolicyTokens, badPortsSet
 const { getGlobalOrigin } = require('./global')
 const { collectASequenceOfCodePoints, collectAnHTTPQuotedString, removeChars, parseMIMEType } = require('./dataURL')
 const { performance } = require('node:perf_hooks')
-const { isBlobLike, toUSVString, ReadableStreamFrom, isValidHTTPToken } = require('../core/util')
+const { isBlobLike, ReadableStreamFrom, isValidHTTPToken } = require('../core/util')
 const assert = require('node:assert')
 const { isUint8Array } = require('util/types')
+const { webidl } = require('./webidl')
 
 // https://nodejs.org/api/crypto.html#determining-if-crypto-support-is-unavailable
 /** @type {import('crypto')|undefined} */
@@ -863,6 +864,75 @@ function createIterator (name, kInternalIterator, keyIndex = 0, valueIndex = 1)
   }
 }
 
+/**
+ * @see https://webidl.spec.whatwg.org/#dfn-iterator-prototype-object
+ * @param {string} name name of the instance
+ * @param {any} object class
+ * @param {symbol} kInternalIterator
+ * @param {string | number} [keyIndex]
+ * @param {string | number} [valueIndex]
+ */
+function iteratorMixin (name, object, kInternalIterator, keyIndex = 0, valueIndex = 1) {
+  const makeIterator = createIterator(name, kInternalIterator, keyIndex, valueIndex)
+
+  const properties = {
+    keys: {
+      writable: true,
+      enumerable: true,
+      configurable: true,
+      value: function keys () {
+        webidl.brandCheck(this, object)
+        return makeIterator(this, 'key')
+      }
+    },
+    values: {
+      writable: true,
+      enumerable: true,
+      configurable: true,
+      value: function values () {
+        webidl.brandCheck(this, object)
+        return makeIterator(this, 'value')
+      }
+    },
+    entries: {
+      writable: true,
+      enumerable: true,
+      configurable: true,
+      value: function entries () {
+        webidl.brandCheck(this, object)
+        return makeIterator(this, 'key+value')
+      }
+    },
+    forEach: {
+      writable: true,
+      enumerable: true,
+      configurable: true,
+      value: function forEach (callbackfn, thisArg = undefined) {
+        webidl.brandCheck(this, object)
+        webidl.argumentLengthCheck(arguments, 1, { header: `${name}.forEach` })
+        if (typeof callbackfn !== 'function') {
+          throw new TypeError(
+            `Failed to execute 'forEach' on '${name}': parameter 1 is not of type 'Function'.`
+          )
+        }
+        for (const { 0: key, 1: value } of createIterator(this, 'key+value')) {
+          callbackfn.call(thisArg, value, key, this)
+        }
+      }
+    }
+  }
+
+  return Object.defineProperties(object.prototype, {
+    ...properties,
+    [Symbol.iterator]: {
+      writable: true,
+      enumerable: false,
+      configurable: true,
+      value: properties.entries.value
+    }
+  })
+}
+
 /**
  * @see https://fetch.spec.whatwg.org/#body-fully-read
  */
@@ -1354,7 +1424,6 @@ module.exports = {
   isCancelled,
   createDeferredPromise,
   ReadableStreamFrom,
-  toUSVString,
   tryUpgradeRequestToAPotentiallyTrustworthyURL,
   clampAndCoarsenConnectionTimingInfo,
   coarsenedSharedCurrentTime,
@@ -1380,6 +1449,7 @@ module.exports = {
   normalizeMethod,
   serializeJavascriptValueToJSONString,
   createIterator,
+  iteratorMixin,
   isValidHeaderName,
   isValidHeaderValue,
   isErrorLike,
diff --git a/lib/fetch/webidl.js b/lib/fetch/webidl.js
index d639b8b7668..a93a25505fc 100644
--- a/lib/fetch/webidl.js
+++ b/lib/fetch/webidl.js
@@ -1,7 +1,7 @@
 'use strict'
 
 const { types } = require('node:util')
-const { toUSVString } = require('./util')
+const { toUSVString } = require('../core/util')
 
 /** @type {import('../../types/webidl').Webidl} */
 const webidl = {}

From 337ff622875235368e3dc34754b58d038e3584e5 Mon Sep 17 00:00:00 2001
From: tsctx <91457664+tsctx@users.noreply.github.com>
Date: Tue, 13 Feb 2024 02:25:54 +0900
Subject: [PATCH 03/13] rename state to object

---
 lib/fetch/util.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/fetch/util.js b/lib/fetch/util.js
index 0737d874c09..935aafe243b 100644
--- a/lib/fetch/util.js
+++ b/lib/fetch/util.js
@@ -769,12 +769,12 @@ function createIterator (name, kInternalIterator, keyIndex = 0, valueIndex = 1)
           `'next' called on an object that does not implement interface ${name} Iterator.`
         )
       }
-      const state = this[kInternalObject]
+      const object = this[kInternalObject]
 
       // 6. Let index be object’s index.
       // 7. Let kind be object’s kind.
       // 8. Let values be object’s target's value pairs to iterate over.
-      const { index, kind, target } = state
+      const { index, kind, target } = object
       const values = target[kInternalIterator]
 
       // 9. Let len be the length of values.
@@ -788,7 +788,7 @@ function createIterator (name, kInternalIterator, keyIndex = 0, valueIndex = 1)
       // 11. Let pair be the entry in values at index index.
       const { [keyIndex]: key, [valueIndex]: value } = values[index]
       // 12. Set object’s index to index + 1.
-      state.index = index + 1
+      object.index = index + 1
       // 13. Return the iterator result for pair and kind.
       // https://webidl.spec.whatwg.org/#iterator-result
       // 1. Let result be a value determined by the value of kind:

From 0962d5a96e39b936c9628cafaca17e47dcc9bd4f Mon Sep 17 00:00:00 2001
From: tsctx <91457664+tsctx@users.noreply.github.com>
Date: Tue, 13 Feb 2024 02:29:17 +0900
Subject: [PATCH 04/13] fixup

---
 lib/fetch/util.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/fetch/util.js b/lib/fetch/util.js
index 935aafe243b..d6a7ab527d6 100644
--- a/lib/fetch/util.js
+++ b/lib/fetch/util.js
@@ -915,7 +915,7 @@ function iteratorMixin (name, object, kInternalIterator, keyIndex = 0, valueInde
             `Failed to execute 'forEach' on '${name}': parameter 1 is not of type 'Function'.`
           )
         }
-        for (const { 0: key, 1: value } of createIterator(this, 'key+value')) {
+        for (const { 0: key, 1: value } of makeIterator(this, 'key+value')) {
           callbackfn.call(thisArg, value, key, this)
         }
       }

From 19a7d8d17ba38e7999112d9cf999dfdb6ded0dc7 Mon Sep 17 00:00:00 2001
From: tsctx <91457664+tsctx@users.noreply.github.com>
Date: Tue, 13 Feb 2024 02:41:27 +0900
Subject: [PATCH 05/13] perf: use class make faster

---
 lib/fetch/util.js | 110 +++++++++++++++++++++++++---------------------
 1 file changed, 59 insertions(+), 51 deletions(-)

diff --git a/lib/fetch/util.js b/lib/fetch/util.js
index d6a7ab527d6..141e653eb99 100644
--- a/lib/fetch/util.js
+++ b/lib/fetch/util.js
@@ -745,37 +745,46 @@ const esIteratorPrototype = Object.getPrototypeOf(Object.getPrototypeOf([][Symbo
  * @param {string | number} [keyIndex]
  * @param {string | number} [valueIndex]
  */
-function createIterator (name, kInternalIterator, keyIndex = 0, valueIndex = 1) {
-  const kInternalObject = Symbol('internal Object')
-
-  // The [[Prototype]] internal slot of an iterator prototype object must be %IteratorPrototype%.
-  const iteratorObject = Object.create(esIteratorPrototype)
+function createFastIterator (name, kInternalIterator, keyIndex = 0, valueIndex = 1) {
+  class FastIterableIterator {
+    /** @type {any} */
+    #target
+    /** @type {'key' | 'value' | 'key+value'} */
+    #kind
+    /** @type {number} */
+    #index
+
+    /**
+     * @see https://webidl.spec.whatwg.org/#dfn-default-iterator-object
+     * @param {unknown} target
+     * @param {'key' | 'value' | 'key+value'} kind
+     */
+    constructor (target, kind) {
+      this.#target = target
+      this.#kind = kind
+      this.#index = 0
+    }
 
-  Object.defineProperty(iteratorObject, 'next', {
-    value: function next () {
+    next () {
       // 1. Let interface be the interface for which the iterator prototype object exists.
-
       // 2. Let thisValue be the this value.
-
       // 3. Let object be ? ToObject(thisValue).
-
       // 4. If object is a platform object, then perform a security
       //    check, passing:
-
       // 5. If object is not a default iterator object for interface,
       //    then throw a TypeError.
-      if (typeof this !== 'object' || this === null || !(kInternalObject in this)) {
+      // Object.getPrototypeOf(this) !== FastIterator.prototype
+      if (typeof this !== 'object' || this === null || !(#target in this)) {
         throw new TypeError(
           `'next' called on an object that does not implement interface ${name} Iterator.`
         )
       }
-      const object = this[kInternalObject]
 
       // 6. Let index be object’s index.
       // 7. Let kind be object’s kind.
       // 8. Let values be object’s target's value pairs to iterate over.
-      const { index, kind, target } = object
-      const values = target[kInternalIterator]
+      const index = this.#index
+      const values = this.#target[kInternalIterator]
 
       // 9. Let len be the length of values.
       const len = values.length
@@ -783,17 +792,25 @@ function createIterator (name, kInternalIterator, keyIndex = 0, valueIndex = 1)
       // 10. If index is greater than or equal to len, then return
       //     CreateIterResultObject(undefined, true).
       if (index >= len) {
-        return { value: undefined, done: true }
+        return {
+          value: undefined,
+          done: true
+        }
       }
+
       // 11. Let pair be the entry in values at index index.
       const { [keyIndex]: key, [valueIndex]: value } = values[index]
+
       // 12. Set object’s index to index + 1.
-      object.index = index + 1
+      this.#index = index + 1
+
       // 13. Return the iterator result for pair and kind.
+
       // https://webidl.spec.whatwg.org/#iterator-result
+
       // 1. Let result be a value determined by the value of kind:
       let result
-      switch (kind) {
+      switch (this.#kind) {
         case 'key':
           // 1. Let idlKey be pair’s key.
           // 2. Let key be the result of converting idlKey to an
@@ -822,45 +839,37 @@ function createIterator (name, kInternalIterator, keyIndex = 0, valueIndex = 1)
           result = [key, value]
           break
       }
+
       // 2. Return CreateIterResultObject(result, false).
       return {
         value: result,
         done: false
       }
-    },
-    writable: true,
-    enumerable: true,
-    configurable: true
-  })
+    }
+  }
+
+  // https://webidl.spec.whatwg.org/#dfn-iterator-prototype-object
+  // @ts-ignore
+  delete FastIterableIterator.prototype.constructor
+
+  Object.setPrototypeOf(FastIterableIterator.prototype, esIteratorPrototype)
 
-  // The class string of an iterator prototype object for a given interface is the
-  // result of concatenating the identifier of the interface and the string " Iterator".
-  Object.defineProperty(iteratorObject, Symbol.toStringTag, {
-    value: `${name} Iterator`,
-    writable: false,
-    enumerable: false,
-    configurable: true
+  Object.defineProperties(FastIterableIterator.prototype, {
+    [Symbol.toStringTag]: {
+      writable: false,
+      enumerable: false,
+      configurable: true,
+      value: `${name} Iterator`
+    },
+    next: { writable: true, enumerable: true, configurable: true }
   })
 
   /**
    * @param {unknown} target
-   * @param {'key'|'value'|'key+value'} kind
+   * @param {'key' | 'value' | 'key+value'} kind
    */
   return function (target, kind) {
-    // esIteratorPrototype needs to be the prototype of iteratorObject
-    // which is the prototype of an empty object. Yes, it's confusing.
-    const iterator = Object.create(iteratorObject)
-    Object.defineProperty(iterator, kInternalObject, {
-      value: {
-        target,
-        kind,
-        index: 0
-      },
-      writable: false,
-      enumerable: false,
-      configurable: true
-    })
-    return iterator
+    return new FastIterableIterator(target, kind)
   }
 }
 
@@ -873,7 +882,7 @@ function createIterator (name, kInternalIterator, keyIndex = 0, valueIndex = 1)
  * @param {string | number} [valueIndex]
  */
 function iteratorMixin (name, object, kInternalIterator, keyIndex = 0, valueIndex = 1) {
-  const makeIterator = createIterator(name, kInternalIterator, keyIndex, valueIndex)
+  const createIterator = createFastIterator(name, kInternalIterator, keyIndex, valueIndex)
 
   const properties = {
     keys: {
@@ -882,7 +891,7 @@ function iteratorMixin (name, object, kInternalIterator, keyIndex = 0, valueInde
       configurable: true,
       value: function keys () {
         webidl.brandCheck(this, object)
-        return makeIterator(this, 'key')
+        return createIterator(this, 'key')
       }
     },
     values: {
@@ -891,7 +900,7 @@ function iteratorMixin (name, object, kInternalIterator, keyIndex = 0, valueInde
       configurable: true,
       value: function values () {
         webidl.brandCheck(this, object)
-        return makeIterator(this, 'value')
+        return createIterator(this, 'value')
       }
     },
     entries: {
@@ -900,7 +909,7 @@ function iteratorMixin (name, object, kInternalIterator, keyIndex = 0, valueInde
       configurable: true,
       value: function entries () {
         webidl.brandCheck(this, object)
-        return makeIterator(this, 'key+value')
+        return createIterator(this, 'key+value')
       }
     },
     forEach: {
@@ -915,7 +924,7 @@ function iteratorMixin (name, object, kInternalIterator, keyIndex = 0, valueInde
             `Failed to execute 'forEach' on '${name}': parameter 1 is not of type 'Function'.`
           )
         }
-        for (const { 0: key, 1: value } of makeIterator(this, 'key+value')) {
+        for (const { 0: key, 1: value } of createIterator(this, 'key+value')) {
           callbackfn.call(thisArg, value, key, this)
         }
       }
@@ -1448,7 +1457,6 @@ module.exports = {
   sameOrigin,
   normalizeMethod,
   serializeJavascriptValueToJSONString,
-  createIterator,
   iteratorMixin,
   isValidHeaderName,
   isValidHeaderValue,

From a68d6775ff5a672f7ec4520f6109342ef5891ead Mon Sep 17 00:00:00 2001
From: tsctx <91457664+tsctx@users.noreply.github.com>
Date: Tue, 13 Feb 2024 02:42:47 +0900
Subject: [PATCH 06/13] fixup

---
 lib/fetch/headers.js | 1 -
 1 file changed, 1 deletion(-)

diff --git a/lib/fetch/headers.js b/lib/fetch/headers.js
index 00a14269f05..87e5669115c 100644
--- a/lib/fetch/headers.js
+++ b/lib/fetch/headers.js
@@ -1,5 +1,4 @@
 // https://github.com/Ethan-Arrowood/undici-fetch
-// https://github.com/Ethan-Arrowood/undici-fetch
 
 'use strict'
 

From 9fdee41006c5acaf9a39aa635fb27eca24776b8a Mon Sep 17 00:00:00 2001
From: tsctx <91457664+tsctx@users.noreply.github.com>
Date: Tue, 13 Feb 2024 02:43:27 +0900
Subject: [PATCH 07/13] fixup

---
 lib/fetch/formdata.js | 5 -----
 lib/fetch/headers.js  | 5 -----
 2 files changed, 10 deletions(-)

diff --git a/lib/fetch/formdata.js b/lib/fetch/formdata.js
index e0a5cf6c199..80df2b8f399 100644
--- a/lib/fetch/formdata.js
+++ b/lib/fetch/formdata.js
@@ -165,11 +165,6 @@ Object.defineProperties(FormData.prototype, {
   getAll: kEnumerableProperty,
   has: kEnumerableProperty,
   set: kEnumerableProperty,
-  // entries: kEnumerableProperty,
-  // keys: kEnumerableProperty,
-  // values: kEnumerableProperty,
-  forEach: kEnumerableProperty,
-  // [Symbol.iterator]: { enumerable: false },
   [Symbol.toStringTag]: {
     value: 'FormData',
     configurable: true
diff --git a/lib/fetch/headers.js b/lib/fetch/headers.js
index 87e5669115c..43860c5d98a 100644
--- a/lib/fetch/headers.js
+++ b/lib/fetch/headers.js
@@ -520,11 +520,6 @@ Object.defineProperties(Headers.prototype, {
   has: kEnumerableProperty,
   set: kEnumerableProperty,
   getSetCookie: kEnumerableProperty,
-  // keys: kEnumerableProperty,
-  // values: kEnumerableProperty,
-  // entries: kEnumerableProperty,
-  forEach: kEnumerableProperty,
-  // [Symbol.iterator]: { enumerable: false },
   [Symbol.toStringTag]: {
     value: 'Headers',
     configurable: true

From e526a4a762f6a9c87d9a0b025edc68ab8c0421dd Mon Sep 17 00:00:00 2001
From: tsctx <91457664+tsctx@users.noreply.github.com>
Date: Tue, 13 Feb 2024 02:46:16 +0900
Subject: [PATCH 08/13] fixup

---
 lib/fetch/util.js | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/lib/fetch/util.js b/lib/fetch/util.js
index 141e653eb99..5156a33d3d7 100644
--- a/lib/fetch/util.js
+++ b/lib/fetch/util.js
@@ -746,7 +746,7 @@ const esIteratorPrototype = Object.getPrototypeOf(Object.getPrototypeOf([][Symbo
  * @param {string | number} [valueIndex]
  */
 function createFastIterator (name, kInternalIterator, keyIndex = 0, valueIndex = 1) {
-  class FastIterableIterator {
+  class FastIterator {
     /** @type {any} */
     #target
     /** @type {'key' | 'value' | 'key+value'} */
@@ -773,7 +773,6 @@ function createFastIterator (name, kInternalIterator, keyIndex = 0, valueIndex =
       //    check, passing:
       // 5. If object is not a default iterator object for interface,
       //    then throw a TypeError.
-      // Object.getPrototypeOf(this) !== FastIterator.prototype
       if (typeof this !== 'object' || this === null || !(#target in this)) {
         throw new TypeError(
           `'next' called on an object that does not implement interface ${name} Iterator.`
@@ -850,11 +849,11 @@ function createFastIterator (name, kInternalIterator, keyIndex = 0, valueIndex =
 
   // https://webidl.spec.whatwg.org/#dfn-iterator-prototype-object
   // @ts-ignore
-  delete FastIterableIterator.prototype.constructor
+  delete FastIterator.prototype.constructor
 
-  Object.setPrototypeOf(FastIterableIterator.prototype, esIteratorPrototype)
+  Object.setPrototypeOf(FastIterator.prototype, esIteratorPrototype)
 
-  Object.defineProperties(FastIterableIterator.prototype, {
+  Object.defineProperties(FastIterator.prototype, {
     [Symbol.toStringTag]: {
       writable: false,
       enumerable: false,
@@ -869,7 +868,7 @@ function createFastIterator (name, kInternalIterator, keyIndex = 0, valueIndex =
    * @param {'key' | 'value' | 'key+value'} kind
    */
   return function (target, kind) {
-    return new FastIterableIterator(target, kind)
+    return new FastIterator(target, kind)
   }
 }
 

From 6d217d60162a00a248e340a7255d8af025126e53 Mon Sep 17 00:00:00 2001
From: tsctx <91457664+tsctx@users.noreply.github.com>
Date: Tue, 13 Feb 2024 02:48:21 +0900
Subject: [PATCH 09/13] fixup

---
 lib/fetch/util.js | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/lib/fetch/util.js b/lib/fetch/util.js
index 5156a33d3d7..5147dfc36f0 100644
--- a/lib/fetch/util.js
+++ b/lib/fetch/util.js
@@ -746,7 +746,7 @@ const esIteratorPrototype = Object.getPrototypeOf(Object.getPrototypeOf([][Symbo
  * @param {string | number} [valueIndex]
  */
 function createFastIterator (name, kInternalIterator, keyIndex = 0, valueIndex = 1) {
-  class FastIterator {
+  class FastIterableIterator {
     /** @type {any} */
     #target
     /** @type {'key' | 'value' | 'key+value'} */
@@ -849,11 +849,11 @@ function createFastIterator (name, kInternalIterator, keyIndex = 0, valueIndex =
 
   // https://webidl.spec.whatwg.org/#dfn-iterator-prototype-object
   // @ts-ignore
-  delete FastIterator.prototype.constructor
+  delete FastIterableIterator.prototype.constructor
 
-  Object.setPrototypeOf(FastIterator.prototype, esIteratorPrototype)
+  Object.setPrototypeOf(FastIterableIterator.prototype, esIteratorPrototype)
 
-  Object.defineProperties(FastIterator.prototype, {
+  Object.defineProperties(FastIterableIterator.prototype, {
     [Symbol.toStringTag]: {
       writable: false,
       enumerable: false,
@@ -866,9 +866,10 @@ function createFastIterator (name, kInternalIterator, keyIndex = 0, valueIndex =
   /**
    * @param {unknown} target
    * @param {'key' | 'value' | 'key+value'} kind
+   * @returns {IterableIterator<any>}
    */
   return function (target, kind) {
-    return new FastIterator(target, kind)
+    return new FastIterableIterator(target, kind)
   }
 }
 

From a7cd726a2ee9bcb73c031ce8b7cdeac12aa42f2d Mon Sep 17 00:00:00 2001
From: tsctx <91457664+tsctx@users.noreply.github.com>
Date: Tue, 13 Feb 2024 02:51:59 +0900
Subject: [PATCH 10/13] fixup

---
 lib/fetch/util.js | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/lib/fetch/util.js b/lib/fetch/util.js
index 5147dfc36f0..82e96ec9acd 100644
--- a/lib/fetch/util.js
+++ b/lib/fetch/util.js
@@ -745,7 +745,7 @@ const esIteratorPrototype = Object.getPrototypeOf(Object.getPrototypeOf([][Symbo
  * @param {string | number} [keyIndex]
  * @param {string | number} [valueIndex]
  */
-function createFastIterator (name, kInternalIterator, keyIndex = 0, valueIndex = 1) {
+function createIterator (name, kInternalIterator, keyIndex = 0, valueIndex = 1) {
   class FastIterableIterator {
     /** @type {any} */
     #target
@@ -882,7 +882,7 @@ function createFastIterator (name, kInternalIterator, keyIndex = 0, valueIndex =
  * @param {string | number} [valueIndex]
  */
 function iteratorMixin (name, object, kInternalIterator, keyIndex = 0, valueIndex = 1) {
-  const createIterator = createFastIterator(name, kInternalIterator, keyIndex, valueIndex)
+  const makeIterator = createIterator(name, kInternalIterator, keyIndex, valueIndex)
 
   const properties = {
     keys: {
@@ -891,7 +891,7 @@ function iteratorMixin (name, object, kInternalIterator, keyIndex = 0, valueInde
       configurable: true,
       value: function keys () {
         webidl.brandCheck(this, object)
-        return createIterator(this, 'key')
+        return makeIterator(this, 'key')
       }
     },
     values: {
@@ -900,7 +900,7 @@ function iteratorMixin (name, object, kInternalIterator, keyIndex = 0, valueInde
       configurable: true,
       value: function values () {
         webidl.brandCheck(this, object)
-        return createIterator(this, 'value')
+        return makeIterator(this, 'value')
       }
     },
     entries: {
@@ -909,14 +909,14 @@ function iteratorMixin (name, object, kInternalIterator, keyIndex = 0, valueInde
       configurable: true,
       value: function entries () {
         webidl.brandCheck(this, object)
-        return createIterator(this, 'key+value')
+        return makeIterator(this, 'key+value')
       }
     },
     forEach: {
       writable: true,
       enumerable: true,
       configurable: true,
-      value: function forEach (callbackfn, thisArg = undefined) {
+      value: function forEach (callbackfn, thisArg = globalThis) {
         webidl.brandCheck(this, object)
         webidl.argumentLengthCheck(arguments, 1, { header: `${name}.forEach` })
         if (typeof callbackfn !== 'function') {
@@ -924,7 +924,7 @@ function iteratorMixin (name, object, kInternalIterator, keyIndex = 0, valueInde
             `Failed to execute 'forEach' on '${name}': parameter 1 is not of type 'Function'.`
           )
         }
-        for (const { 0: key, 1: value } of createIterator(this, 'key+value')) {
+        for (const { 0: key, 1: value } of makeIterator(this, 'key+value')) {
           callbackfn.call(thisArg, value, key, this)
         }
       }
@@ -1458,6 +1458,7 @@ module.exports = {
   normalizeMethod,
   serializeJavascriptValueToJSONString,
   iteratorMixin,
+  createIterator,
   isValidHeaderName,
   isValidHeaderValue,
   isErrorLike,

From 740f1aa6565a765df9eb375c4746577316713b48 Mon Sep 17 00:00:00 2001
From: tsctx <91457664+tsctx@users.noreply.github.com>
Date: Tue, 13 Feb 2024 06:18:16 +0900
Subject: [PATCH 11/13] add test

---
 test/fetch/headers.js | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/test/fetch/headers.js b/test/fetch/headers.js
index b61d8b612d2..44b7d051421 100644
--- a/test/fetch/headers.js
+++ b/test/fetch/headers.js
@@ -472,6 +472,21 @@ test('Headers as Iterable', async (t) => {
 
     deepStrictEqual([...headers], expected)
   })
+
+  await t.test('Headers iterator', (t) => {
+    const HeadersIteratorNext = Function.call.bind(Object.getPrototypeOf(new Headers()[Symbol.iterator]()).next)
+
+    const init = [
+      ['a', '1'],
+      ['b', '2']
+    ]
+
+    const headers = new Headers(init)
+    const iterator = headers[Symbol.iterator]()
+    assert.deepStrictEqual(HeadersIteratorNext(iterator), { value: init[0], done: false })
+    assert.deepStrictEqual(HeadersIteratorNext(iterator), { value: init[1], done: false })
+    assert.deepStrictEqual(HeadersIteratorNext(iterator), { value: undefined, done: true })
+  })
 })
 
 test('arg validation', () => {

From f6f09ad55bec468a0d15e9628b4669332012d384 Mon Sep 17 00:00:00 2001
From: tsctx <91457664+tsctx@users.noreply.github.com>
Date: Tue, 13 Feb 2024 06:19:01 +0900
Subject: [PATCH 12/13] fix test name

---
 test/fetch/headers.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/fetch/headers.js b/test/fetch/headers.js
index 44b7d051421..47987a007df 100644
--- a/test/fetch/headers.js
+++ b/test/fetch/headers.js
@@ -473,7 +473,7 @@ test('Headers as Iterable', async (t) => {
     deepStrictEqual([...headers], expected)
   })
 
-  await t.test('Headers iterator', (t) => {
+  await t.test('always use the same prototype Iterator', (t) => {
     const HeadersIteratorNext = Function.call.bind(Object.getPrototypeOf(new Headers()[Symbol.iterator]()).next)
 
     const init = [

From d9c94abf374230cb681d0e0c5f7a79c75eae5d85 Mon Sep 17 00:00:00 2001
From: tsctx <91457664+tsctx@users.noreply.github.com>
Date: Tue, 13 Feb 2024 06:20:47 +0900
Subject: [PATCH 13/13] simplify

---
 test/fetch/headers.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/fetch/headers.js b/test/fetch/headers.js
index 47987a007df..fcdf4b7a820 100644
--- a/test/fetch/headers.js
+++ b/test/fetch/headers.js
@@ -474,7 +474,7 @@ test('Headers as Iterable', async (t) => {
   })
 
   await t.test('always use the same prototype Iterator', (t) => {
-    const HeadersIteratorNext = Function.call.bind(Object.getPrototypeOf(new Headers()[Symbol.iterator]()).next)
+    const HeadersIteratorNext = Function.call.bind(new Headers()[Symbol.iterator]().next)
 
     const init = [
       ['a', '1'],