perf: improve Headers class performance

benchmarks/fetch/headers-length32.mjs

@@ -40,12 +40,8 @@ const headers = new Headers(
 
 const headersList = getHeadersList(headers)
 
-const kHeadersSortedMap = Reflect.ownKeys(headersList).find(
-  (c) => String(c) === 'Symbol(headers map sorted)'
-)
-
 bench('Headers@@iterator', () => {
-  headersList[kHeadersSortedMap] = null
+  headersList.sortedMap = null
   return [...headers]
 })
 

benchmarks/fetch/headers-methods.mjs

@@ -0,0 +1,70 @@
+import { bench, group, run } from 'mitata'
+import { Headers } from '../../lib/web/fetch/headers.js'
+
+const objectInit = {
+  Accept: 'application/json',
+  'Content-Type': 'text/plain',
+  'User-Agent': 'benchmark',
+  Authorization: 'Bearer token',
+  Cookie: 'a=1',
+  'X-Request-Id': 'abc',
+  'Cache-Control': 'no-cache',
+  Host: 'example.com'
+}
+
+const headers = new Headers(objectInit)
+const copySource = new Headers(objectInit)
+
+group('Headers methods', () => {
+  bench('construct empty', () => {
+    return new Headers()
+  })
+
+  bench('construct object', () => {
+    return new Headers(objectInit)
+  })
+
+  bench('construct headers', () => {
+    return new Headers(copySource)
+  })
+
+  bench('get custom', () => {
+    return headers.get('x-request-id')
+  })
+
+  bench('get common', () => {
+    return headers.get('content-type')
+  })
+
+  bench('has', () => {
+    return headers.has('authorization')
+  })
+
+  bench('set', () => {
+    headers.set('x-count', '1')
+    return headers
+  })
+
+  bench('append', () => {
+    const current = new Headers()
+    current.append('Accept', 'text/html')
+    current.append('X-Custom', '1')
+    return current
+  })
+
+  bench('delete', () => {
+    const current = new Headers(objectInit)
+    current.delete('content-type')
+    return current
+  })
+
+  bench('iterate', () => {
+    let result
+    for (const entry of headers) {
+      result = entry
+    }
+    return result
+  })
+})
+
+await run()

benchmarks/fetch/headers.mjs

@@ -31,20 +31,16 @@ for (const [name, length] of Object.entries(settings)) {
 
   const headersListSorted = getHeadersList(headersSorted)
 
-  const kHeadersSortedMap = Reflect.ownKeys(headersList).find(
-    (c) => String(c) === 'Symbol(headers map sorted)'
-  )
-
   group(`length ${length} #${name}`, () => {
     bench('Headers@@iterator', () => {
       // prevention of memoization of results
-      headersList[kHeadersSortedMap] = null
+      headersList.sortedMap = null
       return [...headers]
     })
 
     bench('Headers@@iterator (sorted)', () => {
       // prevention of memoization of results
-      headersListSorted[kHeadersSortedMap] = null
+      headersListSorted.sortedMap = null
       return [...headersSorted]
     })
   })