perf: Improve FormData

lib/fetch/formdata.js

@@ -61,7 +61,13 @@ class FormData {
 
     // The delete(name) method steps are to remove all entries whose name
     // is name from this’s entry list.
-    this[kState] = this[kState].filter(entry => entry.name !== name)
+    const state = this[kState]
+    for (let i = 0; i < state.length; ++i) {
+      if (state[i].name === name) {
+        state.splice(i, 1)
+        --i
+      }
+    }
   }
 
   get (name) {
@@ -73,14 +79,15 @@ class FormData {
 
     // 1. If there is no entry whose name is name in this’s entry list,
     // then return null.
-    const idx = this[kState].findIndex((entry) => entry.name === name)
-    if (idx === -1) {
-      return null
-    }
-
     // 2. Return the value of the first entry whose name is name from
     // this’s entry list.
-    return this[kState][idx].value
+    const state = this[kState]
+    for (let i = 0; i < state.length; ++i) {
+      if (state[i].name === name) {
+        return state[i].value
+      }
+    }
+    return null
   }
 
   getAll (name) {
@@ -94,9 +101,14 @@ class FormData {
     // then return the empty list.
     // 2. Return the values of all entries whose name is name, in order,
     // from this’s entry list.
-    return this[kState]
-      .filter((entry) => entry.name === name)
-      .map((entry) => entry.value)
+    const state = this[kState]
+    const result = []
+    for (let i = 0; i < state.length; ++i) {
+      if (state[i].name === name) {
+        result.push(state[i].value)
+      }
+    }
+    return result
   }
 
   has (name) {
@@ -108,7 +120,13 @@ class FormData {
 
     // The has(name) method steps are to return true if there is an entry
     // whose name is name in this’s entry list; otherwise false.
-    return this[kState].findIndex((entry) => entry.name === name) !== -1
+    const state = this[kState]
+    for (let i = 0; i < state.length; ++i) {
+      if (state[i].name === name) {
+        return true
+      }
+    }
+    return false
   }
 
   set (name, value, filename = undefined) {
@@ -141,24 +159,31 @@ class FormData {
 
     // 3. If there are entries in this’s entry list whose name is name, then
     // replace the first such entry with entry and remove the others.
-    const idx = this[kState].findIndex((entry) => entry.name === name)
-    if (idx !== -1) {
-      this[kState] = [
-        ...this[kState].slice(0, idx),
-        entry,
-        ...this[kState].slice(idx + 1).filter((entry) => entry.name !== name)
-      ]
-    } else {
+    const state = this[kState]
+    let found = false
+    for (let i = 0; i < state.length; ++i) {
+      if (state[i].name === name) {
+        if (!found) {
+          state[i] = entry
+          found = true
+        } else {
+          state.splice(i, 1)
+          --i
+        }
+      }
+    }
+    if (!found) {
       // 4. Otherwise, append entry to this’s entry list.
-      this[kState].push(entry)
+      state.push(entry)
     }
   }
 
   entries () {
     webidl.brandCheck(this, FormData)
 
+    const state = this[kState]
     return makeIterator(
-      () => this[kState].map(pair => [pair.name, pair.value]),
+      () => getEntiresFromState(state),
       'FormData',
       'key+value'
     )
@@ -167,8 +192,9 @@ class FormData {
   keys () {
     webidl.brandCheck(this, FormData)
 
+    const state = this[kState]
     return makeIterator(
-      () => this[kState].map(pair => [pair.name, pair.value]),
+      () => getEntiresFromState(state),
       'FormData',
       'key'
     )
@@ -177,8 +203,9 @@ class FormData {
   values () {
     webidl.brandCheck(this, FormData)
 
+    const state = this[kState]
     return makeIterator(
-      () => this[kState].map(pair => [pair.name, pair.value]),
+      () => getEntiresFromState(state),
       'FormData',
       'value'
     )
@@ -199,8 +226,11 @@ class FormData {
       )
     }
 
-    for (const [key, value] of this) {
-      callbackFn.apply(thisArg, [value, key, this])
+    // If the state is changed, you can still safely use `for(;;)`
+    // because the value will change.
+    const state = this[kState]
+    for (let i = 0; i < state.length; ++i) {
+      callbackFn.call(thisArg, state[i].value, state[i].name, this)
     }
   }
 }
@@ -262,4 +292,18 @@ function makeEntry (name, value, filename) {
   return { name, value }
 }
 
+/**
+ * @param {unknown} formDataState
+ * @returns {[string, string | File][]}
+ */
+function getEntiresFromState (formDataState) {
+  const stateLength = formDataState.length
+  // Note: avoid `Array#push`
+  const result = new Array(stateLength)
+  for (let i = 0; i < stateLength; ++i) {
+    result[i] = [formDataState[i].name, formDataState[i].value]
+  }
+  return result
+}
+
 module.exports = { FormData }