Add experiment for prefetching (#9747)

vercel · Dec 14, 2019 · 950d67b · 950d67b
1 parent 838aec8
commit 950d67b
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Showing 2 changed files with 10 additions and 3 deletions.
diff --git a/packages/next/build/webpack-config.ts b/packages/next/build/webpack-config.ts
@@ -677,6 +677,9 @@ export default async function getBaseWebpackConfig(
         'process.env.__NEXT_EXPORT_TRAILING_SLASH': JSON.stringify(
           config.exportTrailingSlash
         ),
+        'process.env.__NEXT_PREFETCH_PRELOAD': JSON.stringify(
+          config.experimental.prefetchPreload
+        ),
         'process.env.__NEXT_DEFER_SCRIPTS': JSON.stringify(
           config.experimental.deferScripts
         ),

diff --git a/packages/next/client/page-loader.js b/packages/next/client/page-loader.js
@@ -1,9 +1,13 @@
 /* global document, window */
 import mitt from '../next-server/lib/mitt'
 
+const prefetchOrPreload = process.env.__NEXT_PREFETCH_PRELOAD
+  ? 'prefetch'
+  : 'preload'
+
 function supportsPreload(el) {
   try {
-    return el.relList.supports('preload')
+    return el.relList.supports(prefetchOrPreload)
   } catch {
     return false
   }
@@ -13,7 +17,7 @@ const hasPreload = supportsPreload(document.createElement('link'))
 
 function preloadLink(url, resourceType) {
   const link = document.createElement('link')
-  link.rel = 'preload'
+  link.rel = prefetchOrPreload
   link.crossOrigin = process.crossOrigin
   link.href = url
   link.as = resourceType
@@ -217,7 +221,7 @@ export default class PageLoader {
     // its own deduping mechanism.
     if (
       document.querySelector(
-        `link[rel="preload"][href^="${url}"], script[data-next-page="${route}"]`
+        `link[rel="${prefetchOrPreload}"][href^="${url}"], script[data-next-page="${route}"]`
       )
     ) {
       return