fix: make prefetch do nothing in ssr

Author: egoist

src/index.js

@@ -1,13 +1,11 @@
 import prefetch from './prefetch'
-import { inBrowser } from './utils'
-
-const supported = inBrowser && window.IntersectionObserver
+import { canPrefetch, supportIntersectionObserver } from './utils'
 
 export { prefetch }
 
 export default (Vue, { componentName = 'RouterLink' } = {}) => {
   const observer =
-    supported &&
+    supportIntersectionObserver &&
     new window.IntersectionObserver(entries => {
       entries.forEach(entry => {
         if (entry.isIntersecting) {
@@ -37,10 +35,6 @@ export default (Vue, { componentName = 'RouterLink' } = {}) => {
       }
     },
     mounted() {
-      const conn = navigator.connection
-      const canPrefetch =
-        !conn ||
-        ((conn.effectiveType || '').indexOf('2g') === -1 && !conn.saveData)
       if (this.prefetch && observer && canPrefetch) {
         setTimeout(() => {
           this.observe()

src/prefetch.js

@@ -16,7 +16,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  **/
-import { inBrowser } from './utils'
+import { inBrowser, canPrefetch } from './utils'
 
 const preFetched = {}
 
@@ -102,7 +102,7 @@ const supportedPrefetchStrategy = support('prefetch')
  * @return {Object} a Promise
  */
 function prefetcher(url, isPriority) {
-  if (preFetched[url]) {
+  if (!canPrefetch || preFetched[url]) {
     return
   }
 

src/utils.js

@@ -1 +1,9 @@
 export const inBrowser = typeof window !== 'undefined'
+
+const conn = inBrowser && navigator.connection
+export const canPrefetch =
+  inBrowser &&
+  (!conn || ((conn.effectiveType || '').indexOf('2g') === -1 && !conn.saveData))
+
+export const supportIntersectionObserver =
+  inBrowser && window.IntersectionObserver