Added CROSSORIGIN and eagerness PRERENDER

.size-limit.json

@@ -1,22 +1,22 @@
 [
   {
     "path": "dist/quicklink.js",
-    "limit": "2 kB",
+    "limit": "2.36 kB",
     "gzip": true
   },
   {
     "path": "dist/quicklink.mjs",
-    "limit": "2 kB",
+    "limit": "2.36 kB",
     "gzip": true
   },
   {
     "path": "dist/quicklink.modern.mjs",
-    "limit": "1.6 kB",
+    "limit": "1.91 kB",
     "gzip": true
   },
   {
     "path": "dist/quicklink.umd.js",
-    "limit": "2 kB",
+    "limit": "2.43 kB",
     "gzip": true
   }
-]
+]

package.json

@@ -1,6 +1,6 @@
 {
   "name": "quicklink",
-  "version": "2.3.0",
+  "version": "2.4.0",
   "description": "Faster subsequent page-loads by prefetching in-viewport links during idle time",
   "repository": {
     "type": "git",
@@ -71,4 +71,4 @@
     "size-limit": "^11.1.4",
     "uvu": "^0.5.6"
   }
-}
+}

src/chunks.mjs

@@ -15,7 +15,7 @@
  **/
 
 import throttle from 'throttles';
-import {priority, supported} from './prefetch.mjs';
+import {viaFetch, supported} from './prefetch.mjs';
 import requestIdleCallback from './request-idle-callback.mjs';
 
 // Cache of URLs we've prefetched
@@ -145,7 +145,7 @@ export function prefetch(url, isPriority) {
         // ~> so that we don't repeat broken links
         toPrefetch.add(str);
 
-        return (isPriority ? priority : supported)(
+        return (isPriority ? viaFetch : supported)(
             new URL(str, location.href).toString(),
         );
       }),

src/index.mjs

@@ -15,7 +15,7 @@
  **/
 
 import throttle from 'throttles';
-import {priority, supported} from './prefetch.mjs';
+import {prefetchOnHover, supported, viaFetch} from './prefetch.mjs';
 import requestIdleCallback from './request-idle-callback.mjs';
 import {addSpeculationRules, hasSpecRulesSupport} from './prerender.mjs';
 
@@ -72,6 +72,9 @@ function checkConnection(conn) {
  * @param {Object} options - Configuration options for quicklink
  * @param {Object|Array} [options.el] - DOM element(s) to prefetch in-viewport links of
  * @param {Boolean} [options.priority] - Attempt higher priority fetch (low or high)
+ * @param {Boolean} [options.checkAccessControlAllowOrigin] - Check Access-Control-Allow-Origin response header
+ * @param {Boolean} [options.checkAccessControlAllowCredentials] - Check the Access-Control-Allow-Credentials response header
+ * @param {Boolean} [options.onlyOnMouseover] - Enable the prefetch only on mouseover event
  * @param {Array} [options.origins] - Allowed origins to prefetch (empty allows all)
  * @param {Array|RegExp|Function} [options.ignores] - Custom filter(s) that run after origin checks
  * @param {Number} [options.timeout] - Timeout after which prefetching will occur
@@ -84,6 +87,7 @@ function checkConnection(conn) {
  * @param {Function} [options.hrefFn] - Function to use to build the URL to prefetch.
  *                                             If it's not a valid function, then it will use the entry href.
  * @param {Boolean} [options.prerender] - Option to switch from prefetching and use prerendering only
+ * @param {String} [options.eagerness] - Prerender eagerness mode - default immediate
  * @param {Boolean} [options.prerenderAndPrefetch] - Option to use both prerendering and prefetching
  * @return {Function}
  */
@@ -133,7 +137,7 @@ export function listen(options = {}) {
           // either it's the prerender + prefetch mode or it's prerender *only* mode
           // Prerendering limit is following options.limit. UA may impose arbitraty numeric limit
           if ((shouldPrerenderAndPrefetch || shouldOnlyPrerender) && toPrerender.size < limit) {
-            prerender(hrefFn ? hrefFn(entry) : entry.href).catch(error => {
+            prerender(hrefFn ? hrefFn(entry) : entry.href, options.eagerness).catch(error => {
               if (options.onError) {
                 options.onError(error);
               } else {
@@ -147,7 +151,8 @@ export function listen(options = {}) {
           // Do not prefetch if will match/exceed limit and user has not switched to shouldOnlyPrerender mode
           if (toPrefetch.size < limit && !shouldOnlyPrerender) {
             toAdd(() => {
-              prefetch(hrefFn ? hrefFn(entry) : entry.href, options.priority)
+              prefetch(hrefFn ? hrefFn(entry) : entry.href, options.priority,
+                  options.checkAccessControlAllowOrigin, options.checkAccessControlAllowCredentials, options.onlyOnMouseover)
                   .then(isDone)
                   .catch(error => {
                     isDone();
@@ -156,7 +161,7 @@ export function listen(options = {}) {
             });
           }
         }, delay);
-      // On exit
+        // On exit
       } else {
         entry = entry.target;
         const index = hrefsInViewport.indexOf(entry.href);
@@ -172,9 +177,9 @@ export function listen(options = {}) {
   timeoutFn(() => {
     // Find all links & Connect them to IO if allowed
     const elementsToListen = options.el &&
-    options.el.length &&
-    options.el.length > 0 &&
-    options.el[0].nodeName === 'A' ?
+      options.el.length &&
+      options.el.length > 0 &&
+      options.el[0].nodeName === 'A' ?
       options.el :
       (options.el || document).querySelectorAll('a');
 
@@ -201,10 +206,14 @@ export function listen(options = {}) {
 /**
 * Prefetch a given URL with an optional preferred fetch priority
 * @param {String} url - the URL to fetch
-* @param {Boolean} [isPriority] - if is "high" priority
+* @param {Boolean} isPriority - if is "high" priority
+* @param {Boolean} checkAccessControlAllowOrigin - true to set crossorigin="anonymous" for DOM prefetch
+*                                                    and mode:'cors' for API fetch
+* @param {Boolean} checkAccessControlAllowCredentials - true to set credentials:'include' for API fetch
+* @param {Boolean} onlyOnMouseover - true to enable prefetch only on mouseover event
 * @return {Object} a Promise
 */
-export function prefetch(url, isPriority) {
+export function prefetch(url, isPriority, checkAccessControlAllowOrigin, checkAccessControlAllowCredentials, onlyOnMouseover) {
   const chkConn = checkConnection(navigator.connection);
   if (chkConn instanceof Error) {
     return Promise.reject(new Error(`Cannot prefetch, ${chkConn.message}`));
@@ -223,19 +232,19 @@ export function prefetch(url, isPriority) {
         // ~> so that we don't repeat broken links
         toPrefetch.add(str);
 
-        return (isPriority ? priority : supported)(
-            new URL(str, location.href).toString(),
-        );
+        return prefetchOnHover((isPriority ? viaFetch : supported), new URL(str, location.href).toString(), onlyOnMouseover,
+            checkAccessControlAllowOrigin, checkAccessControlAllowCredentials, isPriority);
       }),
   );
 }
 
 /**
 * Prerender a given URL
 * @param {String} urls - the URL to fetch
+* @param {String} eagerness - prerender eagerness mode - default immediate
 * @return {Object} a Promise
 */
-export function prerender(urls) {
+export function prerender(urls, eagerness = 'immediate') {
   const chkConn = checkConnection(navigator.connection);
   if (chkConn instanceof Error) {
     return Promise.reject(new Error(`Cannot prerender, ${chkConn.message}`));
@@ -245,7 +254,7 @@ export function prerender(urls) {
   // 1) whether UA supports spec rules.. If not, fallback to prefetch
   // Note: Prerendering supports same-site cross origin with opt-in header
   if (!hasSpecRulesSupport()) {
-    prefetch(urls);
+    prefetch(urls, true, false, false, eagerness === 'moderate' || eagerness === 'conservative');
     return Promise.reject(new Error('This browser does not support the speculation rules API. Falling back to prefetch.'));
   }
 
@@ -258,6 +267,6 @@ export function prerender(urls) {
     console.warn('[Warning] You are using both prefetching and prerendering on the same document');
   }
 
-  const addSpecRules = addSpeculationRules(toPrerender);
+  const addSpecRules = addSpeculationRules(toPrerender, eagerness);
   return addSpecRules === true ? Promise.resolve() : Promise.reject(addSpecRules);
 }

src/prefetch.mjs

@@ -20,7 +20,7 @@
 /**
  * Checks if a feature on `link` is natively supported.
  * Examples of features include `prefetch` and `preload`.
- * @param {Object} link Link object.
+ * @param {Object} link - Link object.
  * @return {Boolean} whether the feature is supported
  */
 function hasPrefetch(link) {
@@ -31,13 +31,17 @@ function hasPrefetch(link) {
 /**
  * Fetches a given URL using `<link rel=prefetch>`
  * @param {string} url - the URL to fetch
+ * @param {Boolean} hasCrossorigin - true to set crossorigin="anonymous"
  * @return {Object} a Promise
  */
-function viaDOM(url) {
+function viaDOM(url, hasCrossorigin) {
   return new Promise((resolve, reject, link) => {
     link = document.createElement('link');
     link.rel = 'prefetch';
     link.href = url;
+    if (hasCrossorigin) {
+      link.setAttribute('crossorigin', 'anonymous');
+    }
 
     link.onload = resolve;
     link.onerror = reject;
@@ -49,13 +53,16 @@ function viaDOM(url) {
 /**
  * Fetches a given URL using XMLHttpRequest
  * @param {string} url - the URL to fetch
+ * @param {Boolean} hasCredentials - true to set withCredentials:true
  * @return {Object} a Promise
  */
-function viaXHR(url) {
+function viaXHR(url, hasCredentials) {
   return new Promise((resolve, reject, request) => {
     request = new XMLHttpRequest();
 
-    request.open('GET', url, request.withCredentials = true);
+    request.open('GET', url, request.withCredentials = hasCredentials);
+
+    request.setRequestHeader('Accept', '*/*');
 
     request.onload = () => {
       if (request.status === 200) {
@@ -74,17 +81,61 @@ function viaXHR(url) {
  * Fetches a given URL using the Fetch API. Falls back
  * to XMLHttpRequest if the API is not supported.
  * @param {string} url - the URL to fetch
+ * @param {Boolean} hasModeCors - true to set mode:'cors'
+ * @param {Boolean} hasCredentials - true to set credentials:'include'
+ * @param {Boolean} isPriority - true to set priority:'high'
  * @return {Object} a Promise
  */
-export function priority(url) {
+export function viaFetch(url, hasModeCors, hasCredentials, isPriority) {
   // TODO: Investigate using preload for high-priority
   // fetches. May have to sniff file-extension to provide
   // valid 'as' values. In the future, we may be able to
   // use Priority Hints here.
   //
   // As of 2018, fetch() is high-priority in Chrome
   // and medium-priority in Safari.
-  return window.fetch ? fetch(url, {credentials: 'include'}) : viaXHR(url);
+  const options = {headers: {accept: '*/*'}};
+  if (!hasModeCors) options.mode = 'no-cors';
+  if (hasCredentials) options.credentials = 'include';
+  isPriority ? options.priority = 'high' : options.priority = 'low';
+  return window.fetch ? fetch(url, options) : viaXHR(url, hasCredentials);
+}
+
+/**
+ * Calls the prefetch function immediately
+ * or only on the mouseover event.
+ * @param {Function} callback  - original prefetch function
+ * @param {String} url - url to prefetch
+ * @param {Boolean} onlyOnMouseover - true to add the mouseover listener
+ * @return {Object} a Promise
+ */
+export function prefetchOnHover(callback, url, onlyOnMouseover, ...args) {
+  if (!onlyOnMouseover) return callback(url, ...args);
+
+  const elements = document.querySelectorAll(`a[href="${decodeURIComponent(url)}"]`);
+  const timerMap = new Map();
+
+  for (const el of elements) {
+    const mouseenterListener = e => {
+      const timer = setTimeout(() => {
+        el.removeEventListener('mouseenter', mouseenterListener);
+        el.removeEventListener('mouseleave', mouseleaveListener);
+        return callback(url, ...args);
+      }, 200);
+      timerMap.set(el, timer);
+    };
+
+    const mouseleaveListener = e => {
+      const timer = timerMap.get(el);
+      if (timer) {
+        clearTimeout(timer);
+        timerMap.delete(el);
+      }
+    };
+
+    el.addEventListener('mouseenter', mouseenterListener);
+    el.addEventListener('mouseleave', mouseleaveListener);
+  }
 }
 
-export const supported = hasPrefetch() ? viaDOM : viaXHR;
+export const supported = hasPrefetch() ? viaDOM : viaFetch;

src/prerender.mjs

@@ -20,12 +20,15 @@
 /**
  * Add a given set of urls to the speculation rules
  * @param {Set} urlsToPrerender - the URLs to add to speculation rules
+ * @param {String} eagerness - prerender eagerness mode
  * @return {Boolean|Object}  boolean or Error Object
  */
-export function addSpeculationRules(urlsToPrerender) {
+export function addSpeculationRules(urlsToPrerender, eagerness) {
   const specScript = document.createElement('script');
   specScript.type = 'speculationrules';
-  specScript.text = `{"prerender":[{"source": "list","urls": ["${Array.from(urlsToPrerender).join('","')}"]}]}`;
+  specScript.text = `{"prerender":[{"source": "list",
+                      "urls": ["${Array.from(urlsToPrerender).join('","')}"],
+                      "eagerness": "${eagerness}"}]}`;
   try {
     document.head.appendChild(specScript);
   } catch (error) {