Init

client/.nuxt/components/nuxt-link.client.js

@@ -0,0 +1,98 @@
+import Vue from 'vue'
+
+const requestIdleCallback = window.requestIdleCallback ||
+  function (cb) {
+    const start = Date.now()
+    return setTimeout(function () {
+      cb({
+        didTimeout: false,
+        timeRemaining: () => Math.max(0, 50 - (Date.now() - start))
+      })
+    }, 1)
+  }
+
+const cancelIdleCallback = window.cancelIdleCallback || function (id) {
+  clearTimeout(id)
+}
+
+const observer = window.IntersectionObserver && new window.IntersectionObserver((entries) => {
+  entries.forEach(({ intersectionRatio, target: link }) => {
+    if (intersectionRatio <= 0 || !link.__prefetch) {
+      return
+    }
+    link.__prefetch()
+  })
+})
+
+export default {
+  name: 'NuxtLink',
+  extends: Vue.component('RouterLink'),
+  props: {
+    prefetch: {
+      type: Boolean,
+      default: true
+    },
+    noPrefetch: {
+      type: Boolean,
+      default: false
+    }
+  },
+  mounted () {
+    if (this.prefetch && !this.noPrefetch) {
+      this.handleId = requestIdleCallback(this.observe, { timeout: 2e3 })
+    }
+  },
+  beforeDestroy () {
+    cancelIdleCallback(this.handleId)
+
+    if (this.__observed) {
+      observer.unobserve(this.$el)
+      delete this.$el.__prefetch
+    }
+  },
+  methods: {
+    observe () {
+      // If no IntersectionObserver, avoid prefetching
+      if (!observer) {
+        return
+      }
+      // Add to observer
+      if (this.shouldPrefetch()) {
+        this.$el.__prefetch = this.prefetchLink.bind(this)
+        observer.observe(this.$el)
+        this.__observed = true
+      }
+    },
+    shouldPrefetch () {
+      return this.getPrefetchComponents().length > 0
+    },
+    canPrefetch () {
+      const conn = navigator.connection
+      const hasBadConnection = this.$nuxt.isOffline || (conn && ((conn.effectiveType || '').includes('2g') || conn.saveData))
+
+      return !hasBadConnection
+    },
+    getPrefetchComponents () {
+      const ref = this.$router.resolve(this.to, this.$route, this.append)
+      const Components = ref.resolved.matched.map(r => r.components.default)
+
+      return Components.filter(Component => typeof Component === 'function' && !Component.options && !Component.__prefetched)
+    },
+    prefetchLink () {
+      if (!this.canPrefetch()) {
+        return
+      }
+      // Stop observing this link (in case of internet connection changes)
+      observer.unobserve(this.$el)
+      const Components = this.getPrefetchComponents()
+
+      for (const Component of Components) {
+        const componentOrPromise = Component()
+        if (componentOrPromise instanceof Promise) {
+          componentOrPromise.catch(() => {})
+        }
+        Component.__prefetched = true
+      }
+    }
+  }
+}