perf: optimize Iterator

lib/fetch/formdata.js

@@ -2,9 +2,10 @@
 
 const { isBlobLike, toUSVString, makeIterator } = require('./util')
 const { kState } = require('./symbols')
+const { kEnumerableProperty } = require('../core/util')
 const { File: UndiciFile, FileLike, isFileLike } = require('./file')
 const { webidl } = require('./webidl')
-const { Blob, File: NativeFile } = require('node:buffer')
+const { File: NativeFile } = require('node:buffer')
 
 /** @type {globalThis['File']} */
 const File = NativeFile ?? UndiciFile
@@ -158,29 +159,32 @@ class FormData {
     webidl.brandCheck(this, FormData)
 
     return makeIterator(
-      () => this[kState].map(pair => [pair.name, pair.value]),
+      () => this[kState],
       'FormData',
-      'key+value'
+      'key+value',
+      'name', 'value'
     )
   }
 
   keys () {
     webidl.brandCheck(this, FormData)
 
     return makeIterator(
-      () => this[kState].map(pair => [pair.name, pair.value]),
+      () => this[kState],
       'FormData',
-      'key'
+      'key',
+      'name', 'value'
     )
   }
 
   values () {
     webidl.brandCheck(this, FormData)
 
     return makeIterator(
-      () => this[kState].map(pair => [pair.name, pair.value]),
+      () => this[kState],
       'FormData',
-      'value'
+      'value',
+      'name', 'value'
     )
   }
 
@@ -200,14 +204,25 @@ class FormData {
     }
 
     for (const [key, value] of this) {
-      callbackFn.apply(thisArg, [value, key, this])
+      callbackFn.call(thisArg, value, key, this)
     }
   }
 }
 
 FormData.prototype[Symbol.iterator] = FormData.prototype.entries
 
 Object.defineProperties(FormData.prototype, {
+  append: kEnumerableProperty,
+  delete: kEnumerableProperty,
+  get: kEnumerableProperty,
+  getAll: kEnumerableProperty,
+  has: kEnumerableProperty,
+  set: kEnumerableProperty,
+  entries: kEnumerableProperty,
+  keys: kEnumerableProperty,
+  values: kEnumerableProperty,
+  forEach: kEnumerableProperty,
+  [Symbol.iterator]: { enumerable: false },
   [Symbol.toStringTag]: {
     value: 'FormData',
     configurable: true
@@ -225,7 +240,7 @@ function makeEntry (name, value, filename) {
   // 1. Set name to the result of converting name into a scalar value string.
   // "To convert a string into a scalar value string, replace any surrogates
   //  with U+FFFD."
-  // see: https://nodejs.org/dist/latest-v18.x/docs/api/buffer.html#buftostringencoding-start-end
+  // see: https://nodejs.org/dist/latest-v20.x/docs/api/buffer.html#buftostringencoding-start-end
   name = Buffer.from(name).toString('utf8')
 
   // 2. If value is a string, then set value to the result of converting

lib/fetch/headers.js

@@ -492,48 +492,33 @@ class Headers {
   keys () {
     webidl.brandCheck(this, Headers)
 
-    if (this[kGuard] === 'immutable') {
-      const value = this[kHeadersSortedMap]
-      return makeIterator(() => value, 'Headers',
-        'key')
-    }
-
     return makeIterator(
-      () => [...this[kHeadersSortedMap].values()],
+      () => this[kHeadersSortedMap],
       'Headers',
-      'key'
+      'key',
+      0, 1
     )
   }
 
   values () {
     webidl.brandCheck(this, Headers)
 
-    if (this[kGuard] === 'immutable') {
-      const value = this[kHeadersSortedMap]
-      return makeIterator(() => value, 'Headers',
-        'value')
-    }
-
     return makeIterator(
-      () => [...this[kHeadersSortedMap].values()],
+      () => this[kHeadersSortedMap],
       'Headers',
-      'value'
+      'value',
+      0, 1
     )
   }
 
   entries () {
     webidl.brandCheck(this, Headers)
 
-    if (this[kGuard] === 'immutable') {
-      const value = this[kHeadersSortedMap]
-      return makeIterator(() => value, 'Headers',
-        'key+value')
-    }
-
     return makeIterator(
-      () => [...this[kHeadersSortedMap].values()],
+      () => this[kHeadersSortedMap],
       'Headers',
-      'key+value'
+      'key+value',
+      0, 1
     )
   }
 
@@ -553,7 +538,7 @@ class Headers {
     }
 
     for (const [key, value] of this) {
-      callbackFn.apply(thisArg, [value, key, this])
+      callbackFn.call(thisArg, value, key, this)
     }
   }
 

lib/fetch/util.js

@@ -739,19 +739,23 @@ const esIteratorPrototype = Object.getPrototypeOf(Object.getPrototypeOf([][Symbo
 
 /**
  * @see https://webidl.spec.whatwg.org/#dfn-iterator-prototype-object
- * @param {() => unknown[]} iterator
+ * @param {() => unknown} iterator
  * @param {string} name name of the instance
  * @param {'key'|'value'|'key+value'} kind
+ * @param {string | number} [keyIndex]
+ * @param {string | number} [valueIndex]
  */
-function makeIterator (iterator, name, kind) {
+function makeIterator (iterator, name, kind, keyIndex = 0, valueIndex = 1) {
   const object = {
     index: 0,
     kind,
     target: iterator
   }
+  // The [[Prototype]] internal slot of an iterator prototype object must be %IteratorPrototype%.
+  const iteratorObject = Object.create(esIteratorPrototype)
 
-  const i = {
-    next () {
+  Object.defineProperty(iteratorObject, 'next', {
+    value: function next () {
       // 1. Let interface be the interface for which the iterator prototype object exists.
 
       // 2. Let thisValue be the this value.
@@ -763,7 +767,7 @@ function makeIterator (iterator, name, kind) {
 
       // 5. If object is not a default iterator object for interface,
       //    then throw a TypeError.
-      if (Object.getPrototypeOf(this) !== i) {
+      if (Object.getPrototypeOf(this) !== iteratorObject) {
         throw new TypeError(
           `'next' called on an object that does not implement interface ${name} Iterator.`
         )
@@ -783,68 +787,62 @@ function makeIterator (iterator, name, kind) {
       if (index >= len) {
         return { value: undefined, done: true }
       }
-
       // 11. Let pair be the entry in values at index index.
-      const pair = values[index]
-
+      const { [keyIndex]: key, [valueIndex]: value } = values[index]
       // 12. Set object’s index to index + 1.
       object.index = index + 1
-
       // 13. Return the iterator result for pair and kind.
-      return iteratorResult(pair, kind)
+      // https://webidl.spec.whatwg.org/#iterator-result
+      // 1. Let result be a value determined by the value of kind:
+      let result
+      if (kind === 'key') {
+        // 1. Let idlKey be pair’s key.
+        // 2. Let key be the result of converting idlKey to an
+        //    ECMAScript value.
+        // 3. result is key.
+        result = key
+      } else if (kind === 'value') {
+        // 1. Let idlValue be pair’s value.
+        // 2. Let value be the result of converting idlValue to
+        //    an ECMAScript value.
+        // 3. result is value.
+        result = value
+      } else {
+        // 1. Let idlKey be pair’s key.
+        // 2. Let idlValue be pair’s value.
+        // 3. Let key be the result of converting idlKey to an
+        //    ECMAScript value.
+        // 4. Let value be the result of converting idlValue to
+        //    an ECMAScript value.
+        // 5. Let array be ! ArrayCreate(2).
+        // 6. Call ! CreateDataProperty(array, "0", key).
+        // 7. Call ! CreateDataProperty(array, "1", value).
+        // 8. result is array.
+        result = [key, value]
+      }
+      // 2. Return CreateIterResultObject(result, false).
+      return {
+        value: result,
+        done: false
+      }
     },
-    // 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".
-    [Symbol.toStringTag]: `${name} Iterator`
-  }
-
-  // The [[Prototype]] internal slot of an iterator prototype object must be %IteratorPrototype%.
-  Object.setPrototypeOf(i, esIteratorPrototype)
-  // esIteratorPrototype needs to be the prototype of i
-  // which is the prototype of an empty object. Yes, it's confusing.
-  return Object.setPrototypeOf({}, i)
-}
+    writable: true,
+    enumerable: true,
+    configurable: true
+  })
 
-// https://webidl.spec.whatwg.org/#iterator-result
-function iteratorResult (pair, kind) {
-  let result
-
-  // 1. Let result be a value determined by the value of kind:
-  switch (kind) {
-    case 'key': {
-      // 1. Let idlKey be pair’s key.
-      // 2. Let key be the result of converting idlKey to an
-      //    ECMAScript value.
-      // 3. result is key.
-      result = pair[0]
-      break
-    }
-    case 'value': {
-      // 1. Let idlValue be pair’s value.
-      // 2. Let value be the result of converting idlValue to
-      //    an ECMAScript value.
-      // 3. result is value.
-      result = pair[1]
-      break
-    }
-    case 'key+value': {
-      // 1. Let idlKey be pair’s key.
-      // 2. Let idlValue be pair’s value.
-      // 3. Let key be the result of converting idlKey to an
-      //    ECMAScript value.
-      // 4. Let value be the result of converting idlValue to
-      //    an ECMAScript value.
-      // 5. Let array be ! ArrayCreate(2).
-      // 6. Call ! CreateDataProperty(array, "0", key).
-      // 7. Call ! CreateDataProperty(array, "1", value).
-      // 8. result is array.
-      result = pair
-      break
-    }
-  }
+  // 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
+  })
 
-  // 2. Return CreateIterResultObject(result, false).
-  return { value: result, done: false }
+  // esIteratorPrototype needs to be the prototype of iteratorObject
+  // which is the prototype of an empty object. Yes, it's confusing.
+  return Object.create(iteratorObject)
 }
 
 /**

package.json

@@ -121,7 +121,7 @@
     "jest": "^29.0.2",
     "jsdom": "^24.0.0",
     "jsfuzz": "^1.0.15",
-    "mitata": "^0.1.6",
+    "mitata": "^0.1.8",
     "mocha": "^10.0.0",
     "p-timeout": "^3.2.0",
     "pre-commit": "^1.2.2",