import Vue from 'vue' import VueMeta from 'vue-meta' import VueServerRenderer from 'vue-server-renderer' import LRU from 'lru-cache' export default class MetaRenderer { constructor (nuxt, renderer) { this.nuxt = nuxt this.renderer = renderer this.options = nuxt.options this.vueRenderer = VueServerRenderer.createRenderer() this.cache = LRU({}) // Add VueMeta to Vue (this is only for SPA mode) // See lib/app/index.js Vue.use(VueMeta, { keyName: 'head', attribute: 'data-n-head', ssrAttribute: 'data-n-head-ssr', tagIDKeyName: 'hid' }) } getMeta (url) { return new Promise((resolve, reject) => { const vm = new Vue({ render: (h) => h(), // Render empty html tag head: this.options.head || {} }) this.vueRenderer.renderToString(vm, (err) => { if (err) return reject(err) resolve(vm.$meta().inject()) }) }) } async render ({ url = '/' }) { let meta = this.cache.get(url) if (meta) { return meta } meta = { HTML_ATTRS: '', BODY_ATTRS: '', HEAD: '' } // Get vue-meta context const m = await this.getMeta(url) // HTML_ATTRS meta.HTML_ATTRS = m.htmlAttrs.text() // BODY_ATTRS meta.BODY_ATTRS = m.bodyAttrs.text() // HEAD tags meta.HEAD = m.meta.text() + m.title.text() + m.link.text() + m.style.text() + m.script.text() + m.noscript.text() // Resources Hints meta.resourceHints = '' // Resource Hints const clientManifest = this.renderer.resources.clientManifest if (this.options.render.resourceHints && clientManifest) { const publicPath = clientManifest.publicPath || '/_nuxt/' // Pre-Load initial resources if (Array.isArray(clientManifest.initial)) { meta.resourceHints += clientManifest.initial.map(r => ``).join('') } // Pre-Fetch async resources if (Array.isArray(clientManifest.async)) { meta.resourceHints += clientManifest.async.map(r => ``).join('') } // Add them to HEAD if (meta.resourceHints) { meta.HEAD += meta.resourceHints } } // Set meta tags inside cache this.cache.set(url, meta) return meta } }