Clean-up source

package.json

@@ -2,7 +2,7 @@
   "name": "quicklink",
   "version": "0.0.1",
   "description": "Faster page-loads by prefetching links during idle time",
-  "main": "index.js",
+  "main": "src/index.mjs",
   "repository": "/~https://github.com/addyosmani/quicklink.git",
   "author": "addyosmani <addyosmani@gmail.com>",
   "license": "Apache-2.0",

index.mjs → src/index.mjs

@@ -1,3 +1,6 @@
+import prefetch from './prefetch.mjs';
+import requestIdleCallback from './request-idle-callback.mjs';
+
 /**
  * 
  * @param urls Array of URLs to prefetch
@@ -63,6 +66,4 @@ export default function quicklink(options) {
             });
         }
     });
-}
-
-// TODO: add preload / high prio?
+}

src/prefetch.mjs

@@ -0,0 +1,47 @@
+const support = function(feature) {
+  if (typeof document === `undefined`) {
+    return false
+  }
+  const fakeLink = document.createElement(`link`)
+  try {
+    if (fakeLink.relList && typeof fakeLink.relList.supports === `function`) {
+      return fakeLink.relList.supports(feature)
+    }
+  } catch (err) {
+    return false
+  }
+}
+const linkPrefetchStrategy = function(url) {
+  if (typeof document === `undefined`) {
+    return
+  }
+  const link = document.createElement(`link`)
+  link.setAttribute(`rel`, `prefetch`)
+  link.setAttribute(`href`, url)
+  const parentElement =
+    document.getElementsByTagName(`head`)[0] ||
+    document.getElementsByName(`script`)[0].parentNode
+  parentElement.appendChild(link)
+}
+const xhrPrefetchStrategy = function(url) {
+  const req = new XMLHttpRequest()
+  req.open(`GET`, url, true)
+  req.withCredentials = true
+  req.send(null)
+}
+
+const supportedPrefetchStrategy = support(`prefetch`)
+  ? linkPrefetchStrategy
+  : xhrPrefetchStrategy
+
+const preFetched = {}
+
+const prefetch = function(url) {
+  if (preFetched[url]) {
+    return
+  }
+  preFetched[url] = true
+  supportedPrefetchStrategy(url)
+}
+
+export default prefetch

src/request-idle-callback.mjs

@@ -0,0 +1,15 @@
+// RIC and shim for browsers setTimeout() without it
+const requestIdleCallback = window.requestIdleCallback ||
+  function (cb) {
+    let start = Date.now();
+    return setTimeout(function () {
+      cb({
+        didTimeout: false,
+        timeRemaining: function () {
+          return Math.max(0, 50 - (Date.now() - start));
+        }
+      });
+    }, 1);
+  }
+
+export default requestIdleCallback;