Nuxt/packages/vue-app/template/components/nuxt-link.client.js

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<%= isTest ? '// @vue/component' : '' %>
import Vue from 'vue'
const requestIdleCallback = window.requestIdleCallback ||
function (cb) {
const start = Date.now()
return setTimeout(function () {
cb({
didTimeout: false,
timeRemaining: function () {
return Math.max(0, 50 - (Date.now() - start))
},
})
}, 1)
}
const observer = window.IntersectionObserver && new window.IntersectionObserver(entries => {
entries.forEach(({ intersectionRatio, target: link }) => {
if (intersectionRatio <= 0) {
return
}
link.__prefetch()
})
})
export default {
extends: Vue.component('RouterLink'),
name: 'NuxtLink',
props: {
noPrefetch: {
type: Boolean,
default: false
}<% if (router.linkPrefetchedClass) { %>,
prefetchedClass: {
type: String,
default: '<%= router.linkPrefetchedClass %>'
}<% } %>
},
mounted() {
if (!this.noPrefetch) {
requestIdleCallback(this.observe, { timeout: 2e3 })
}
},
beforeDestroy() {
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.$el.__prefetch = this.prefetch.bind(this)
observer.observe(this.$el)
this.__observed = true
}<% if (router.linkPrefetchedClass) { %> else {
this.addPrefetchedClass()
}<% } %>
},
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.$route, this.append)
const Components = ref.resolved.matched.map((r) => r.components.default)
return Components.filter((Component) => typeof Component === 'function' && !Component.options && !Component.__prefetched)
},
prefetch() {
if (!this.canPrefetch()) {
return
}
// Stop obersing this link (in case of internet connection changes)
observer.unobserve(this.$el)
const Components = this.getPrefetchComponents()
for (const Component of Components) {
try {
Component()
Component.__prefetched = true
} catch (e) {}
}<% if (router.linkPrefetchedClass) { %>
this.addPrefetchedClass()<% } %>
}<% if (router.linkPrefetchedClass) { %>,
addPrefetchedClass() {
if (this.prefetchedClass !== 'false') {
this.$el.className += (this.$el.className + ' ' + this.prefetchedClass).trim()
}
}<% } %>
}
}