Update head-manager to compress better

packages/next/client/head-manager.js

@@ -5,90 +5,6 @@ const DOMAttributeNames = {
   httpEquiv: 'http-equiv',
 }
 
-export default class HeadManager {
-  constructor() {
-    this.updatePromise = null
-  }
-
-  updateHead = head => {
-    const promise = (this.updatePromise = Promise.resolve().then(() => {
-      if (promise !== this.updatePromise) return
-
-      this.updatePromise = null
-      this.doUpdateHead(head)
-    }))
-  }
-
-  doUpdateHead(head) {
-    const tags = {}
-    head.forEach(h => {
-      const components = tags[h.type] || []
-      components.push(h)
-      tags[h.type] = components
-    })
-
-    this.updateTitle(tags.title ? tags.title[0] : null)
-
-    const types = ['meta', 'base', 'link', 'style', 'script']
-    types.forEach(type => {
-      this.updateElements(type, tags[type] || [])
-    })
-  }
-
-  updateTitle(component) {
-    let title = ''
-    if (component) {
-      const { children } = component.props
-      title = typeof children === 'string' ? children : children.join('')
-    }
-    if (title !== document.title) document.title = title
-  }
-
-  updateElements(type, components) {
-    const headEl = document.getElementsByTagName('head')[0]
-    const headCountEl = headEl.querySelector('meta[name=next-head-count]')
-    if (process.env.NODE_ENV !== 'production') {
-      if (!headCountEl) {
-        console.error(
-          'Warning: next-head-count is missing. https://err.sh/next.js/next-head-count-missing'
-        )
-        return
-      }
-    }
-
-    const headCount = Number(headCountEl.content)
-    const oldTags = []
-
-    for (
-      let i = 0, j = headCountEl.previousElementSibling;
-      i < headCount;
-      i++, j = j.previousElementSibling
-    ) {
-      if (j.tagName.toLowerCase() === type) {
-        oldTags.push(j)
-      }
-    }
-    const newTags = components.map(reactElementToDOM).filter(newTag => {
-      for (let k = 0, len = oldTags.length; k < len; k++) {
-        const oldTag = oldTags[k]
-        if (oldTag.isEqualNode(newTag)) {
-          oldTags.splice(k, 1)
-          return false
-        }
-      }
-      return true
-    })
-
-    oldTags.forEach(t => t.parentNode.removeChild(t))
-    newTags.forEach(t => headEl.insertBefore(t, headCountEl))
-    headCountEl.content = (
-      headCount -
-      oldTags.length +
-      newTags.length
-    ).toString()
-  }
-}
-
 function reactElementToDOM({ type, props }) {
   const el = document.createElement(type)
   for (const p in props) {
@@ -110,3 +26,73 @@ function reactElementToDOM({ type, props }) {
   }
   return el
 }
+
+function updateElements(type, components) {
+  const headEl = document.getElementsByTagName('head')[0]
+  const headCountEl = headEl.querySelector('meta[name=next-head-count]')
+  if (process.env.NODE_ENV !== 'production') {
+    if (!headCountEl) {
+      console.error(
+        'Warning: next-head-count is missing. https://err.sh/next.js/next-head-count-missing'
+      )
+      return
+    }
+  }
+
+  const headCount = Number(headCountEl.content)
+  const oldTags = []
+
+  for (
+    let i = 0, j = headCountEl.previousElementSibling;
+    i < headCount;
+    i++, j = j.previousElementSibling
+  ) {
+    if (j.tagName.toLowerCase() === type) {
+      oldTags.push(j)
+    }
+  }
+  const newTags = components.map(reactElementToDOM).filter(newTag => {
+    for (let k = 0, len = oldTags.length; k < len; k++) {
+      const oldTag = oldTags[k]
+      if (oldTag.isEqualNode(newTag)) {
+        oldTags.splice(k, 1)
+        return false
+      }
+    }
+    return true
+  })
+
+  oldTags.forEach(t => t.parentNode.removeChild(t))
+  newTags.forEach(t => headEl.insertBefore(t, headCountEl))
+  headCountEl.content = (headCount - oldTags.length + newTags.length).toString()
+}
+
+export default function initHeadManager() {
+  let updatePromise = null
+
+  return head => {
+    const promise = (updatePromise = Promise.resolve().then(() => {
+      if (promise !== updatePromise) return
+
+      updatePromise = null
+      const tags = {}
+
+      head.forEach(h => {
+        const components = tags[h.type] || []
+        components.push(h)
+        tags[h.type] = components
+      })
+
+      const titleComponent = tags.title ? tags.title[0] : null
+      let title = ''
+      if (titleComponent) {
+        const { children } = titleComponent.props
+        title = typeof children === 'string' ? children : children.join('')
+      }
+      if (title !== document.title) document.title = title
+      ;['meta', 'base', 'link', 'style', 'script'].forEach(type => {
+        updateElements(type, tags[type] || [])
+      })
+    }))
+  }
+}

packages/next/client/index.js

@@ -1,7 +1,7 @@
 /* global location */
 import React from 'react'
 import ReactDOM from 'react-dom'
-import HeadManager from './head-manager'
+import initHeadManager from './head-manager'
 import { createRouter, makePublicRouterInstance } from 'next/router'
 import mitt from '../next-server/lib/mitt'
 import { loadGetInitialProps, getURL, ST } from '../next-server/lib/utils'
@@ -57,7 +57,7 @@ if (window.__NEXT_P) {
 window.__NEXT_P = []
 window.__NEXT_P.push = register
 
-const headManager = new HeadManager()
+const updateHead = initHeadManager()
 const appElement = document.getElementById('__next')
 
 let lastAppProps
@@ -397,7 +397,7 @@ function AppContainer({ children }) {
       }
     >
       <RouterContext.Provider value={makePublicRouterInstance(router)}>
-        <HeadManagerContext.Provider value={headManager.updateHead}>
+        <HeadManagerContext.Provider value={updateHead}>
           {children}
         </HeadManagerContext.Provider>
       </RouterContext.Provider>

test/integration/size-limit/test/index.test.js

@@ -80,7 +80,7 @@ describe('Production response size', () => {
     )
 
     // These numbers are without gzip compression!
-    const delta = responseSizesBytes - 238 * 1024
+    const delta = responseSizesBytes - 237 * 1024
     expect(delta).toBeLessThanOrEqual(1024) // don't increase size more than 1kb
     expect(delta).toBeGreaterThanOrEqual(-1024) // don't decrease size more than 1kb without updating target
   })