🔌⚡ Nuxt Prune HTML

Nuxt module to prune html before sending it to the browser (it removes elements matching CSS selector(s)), useful for boosting performance showing a different HTML for bots/audits by removing all the scripts with dynamic rendering.

💘 Motivation

Due to the versatility of Nuxt (and of the SSR in general), a website generated (or served) via node server, has everything it needs already injected in the HTML (ex. css styles). So, usually, for a bot, a audit or for a human, the website its almost visually the same with or without Javascript.

This library is born to remove all the scripts injected into the HTML only if a visitor is a Bot or a Performance Audit (ex. a Lighthouse Audit). This should speed up (blazing fast) your nuxt-website up to a value of ~99 in performance because it cheats various scenarios.

Usually, with less assets, resources and html to download, the number of urls crawled by a bot are widely boosted 📈.

Inspired by this rcfs and this issue.

Features

• Prune based on default detection;
  • match the user-agent;
  • match a bot;
  • match an audit;
  • match a custom-header;
• Prune based on headers values (useful in/for Lambdas);
• Prune based on query parameters (useful during navigation, hybrid-experience).

Pro et contra

This could cause some unexpected behaviors, but..

Cons.:

• No SPA routing on client-side for bots and audits;
• No hydration on client-side for bots and audits:
  • ex. vue-lazy-hydration need Javascript client-side code to trigger hydrateOnInteraction, hydrateWhenIdle or hydrateWhenVisible;
• No <client-only> components;
• Can break lazy-load for images.

Pros.:

• Some of these features aren't "used by" a bot/audit, so you don't really need them:
  • bots doesn't handle SPA routing;
  • <client-only> components could lead in a slower TTI;
  • <client-only> components can contain a static placeholder;
• Images with lazy-load can be fixed with a native attribute, with a custom script or with classesSelectorsToKeep (check the configuration);
• You can pre-load ad inject all of the data that you need (Rest API, GraphQL, ecc) during the build phase with nuxt-apis-to-file, speeding up the website loading time;
• Hydration decrease performance, so it's ok to prune it for bots or audits;
• Less HTML, assets and resources are served to browsers and clients;
• Bot/audit only have the Javascript they need;
• With less assets to download, the number of urls crawled are widely boosted;
• Bots, PageSpeed Insights, Google Measure and Lighthouse Audit are already pruned by the plugin with the default configuration;
• Faster web-vitals, faster TTI, faster FCP, faster FMP, faster all.

N.B.: This is known as Dynamic Rendering and it's not considered black-hat or cloaking.

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💡 Lighthouse

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Setup

1. Install @luxdamore/nuxt-prune-html as a dependency:
   • yarn add @luxdamore/nuxt-prune-html;
   • or, npm install --save @luxdamore/nuxt-prune-html;
2. Append @luxdamore/nuxt-prune-html to the modules array of your nuxt.config.js.

Configuration

    // nuxt.config.js
    export default {

        // Module - installation
        modules: [ '@luxdamore/nuxt-prune-html' ],

        // Module - default config
        pruneHtml: {
            enabled: false, // `true` in production
            hideGenericMessagesInConsole: false, // `false` in production
            hideErrorsInConsole: false, // deactivate the `console.error` method
            hookRenderRoute: true, // activate `hook:render:route`
            hookGeneratePage: true, // activate `hook:generate:page`
            selectors: [
                // CSS selectors to prune
                'link[rel="preload"][as="script"]',
                'script:not([type="application/ld+json"])',
            ],
            classesSelectorsToKeep: [], // disallow pruning of scripts with this classes, n.b.: each `classesSelectorsToKeep` is appended to every `selectors`, ex.: `link[rel="preload"][as="script"]:not(__classesSelectorsToKeep__)`
            link: [], // inject custom links, only if pruned
            script: [], // inject custom scripts, only if pruned
            htmlElementClass: null, // a string added as a class to the <html> element if pruned
            cheerio: {
                // the config passed to the `cheerio.load(__config__)` method
                xmlMode: false,
            },
            types: [
                // it's possibile to add different rules for pruning
                'default-detect',
            ],

            // 👇🏻 Type: `default-detect`
            headerNameForDefaultDetection: 'user-agent', // The `header-key` base for `MobileDetection`, usage `request.headers[ headerNameForDefaultDetection ]`
            auditUserAgent: 'lighthouse', // prune if `request.header[ headerNameForDefaultDetection ]` match, could be a string or an array of strings
            isAudit: true, // remove selectors if match with `auditUserAgent`
            isBot: true, // remove selectors if is a bot
            ignoreBotOrAudit: false, // remove selectors in any case, not depending on Bot or Audit
            matchUserAgent: null, // prune if `request.header[ headerNameForDefaultDetection ]` match, could be a string or an array of strings

            // 👇🏻 Type: 'query-parameters'
            queryParametersToPrune: [
                // array of objects (key-value)
                // trigger the pruning if 'query-parameters' is present in `types` and at least one value is matched, ex. `/?prune=true`
                {
                    key: 'prune',
                    value: 'true',
                },
            ],
            queryParametersToExcludePrune: [], // same as `queryParametersToPrune`, exclude the pruning if 'query-parameters' is present in `types` and at least one value is matched, this priority is over than `queryParametersToPrune`

            // 👇🏻 Type: 'headers-exist'
            headersToPrune: [], // same as `queryParametersToPrune`, but it checks `request.headers`
            headersToExcludePrune: [], // same as `queryParamToExcludePrune`, but it checks `request.headers`, this priority is over than `headersToPrune`

            // Emitted events for callbacks methods
            onBeforePrune: null, // ({ result, [ req, res ] }) => {}, `req` and `res` are not available on `nuxt generate`
            onAfterPrune: null, // ({ result, [ req, res ] }) => {}, `req` and `res` are not available on `nuxt generate`
        },

    };

With link and script it's possibile to add one or more objects on the pruned HTML, ex.:

    export default {
        pruneHtml: {
            link: [
                {
                    rel: 'preload',
                    as: 'script',
                    href: '/my-custom-lazy-load-for-bots.js',
                    position: 'phead', // Default value is 'body', other allowed values are: 'phead', 'head' and 'pbody'
                },
                {
                    rel: 'stylesheet',
                    href: '/my-custom-styles-for-bots.css',
                    position: 'head',
                },
            ],
            script: [
                {
                    src: '/my-custom-lazy-load-for-bots.js',
                    lazy: true,
                    defer: true,
                },
            ],
        },
    };

N.B.: the config is only shallow merged, not deep merged.

Types / Rules

Possible values are [ 'default-detect', 'query-parameters', 'headers-exist' ]:

• default-detect: prune based on one header(request.headers[ headerNameForDefaultDetection ])
  • different checks with MobileDetect:
    • isBot, trigger .is( 'bot' ) method;
    • auditUserAgent or matchUserAgent, trigger .match() method;
• query-parameters: prune based on one or more query parameter, tests key / value based on queryParametersToPrune / queryParametersToExcludePrune:
  • you can also specify routes in nuxt.config, ex. { generate: { routes: [ '/?prune=true' ] } }
• headers-exist: prune based on one or more header, tests key / value based on headersToPrune / headersToExcludePrune.

N.B.: It's possibile to mix different types.

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Related things you should know

• Nuxt hooks, the plugin has access to request.headers only if the project is running as a server (ex. nuxt start)
  • If you generate your site it's not possibile to check request.headers, so (for types: [ 'default-detect', 'headers-exist' ]) it always prune, but You can disable this behavior by setting hookGeneratePage to false (or by using the type query-parameters);
• Usage with types: [ 'default-detect' ], load the MobileDetect library;
• It use Cheerio, jQuery for servers, library to filter and prune the html.

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Advices

• Before setting up the module, try to Disable JavaScript With Chrome DevTools while navigate your website, this is how your website appear (when nuxt-prune-html is enabled);
• For <client-only> components you should prepare a version that is visually the same with the placeholder slot;
• You can check the website as a GoogleBot, following this guide;
• The nuxt-apis-to-file module can help you with data payload extraction during the build time.

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👩🏻‍💻👨🏻‍💻 Development

1. Clone the repository:
   • git clone https://github.com/LuXDAmore/nuxt-prune-html.git;
2. Install dependencies:
   • yarn install (or npm install);
3. Start a development server:
   • yarn dev (or npm run dev);
4. Test your code:
   • yarn test (or npm run test);
5. Extra, generate the documentation (Github Pages):
   • yarn generate (or npm run generate);
   • the content is automatically generated into the /docs folder.

🐞 Issues

Please make sure to read the issue reporting checklist before opening an issue. Issues not conforming to the guidelines may be closed immediately.

📝 Discussions

We're using Github discussions as a place to connect with other members of our community. You are free to ask questions and share ideas, so enjoy yourself.

👥 Contribution

Please make sure to read the contributing guide before making a pull request.

📖 Changelog

Details changes for each release are documented in the release notes.

🆓 License

MIT License // Copyright (©) 2019-now Luca Iaconelli

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