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82 lines
3.8 KiB
Markdown
82 lines
3.8 KiB
Markdown
---
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title: "How Nuxt Works?"
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description: "Nuxt is a minimal but highly customizable framework to build web applications."
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---
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This guide helps you better understand Nuxt internals to develop new solutions and module integrations on top of Nuxt.
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## The Nuxt Interface
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When you start Nuxt in development mode with [`nuxi dev`](/docs/api/commands/dev) or building a production application with [`nuxi build`](/docs/api/commands/build),
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a common context will be created, referred to as `nuxt` internally. It holds normalized options merged with `nuxt.config` file,
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some internal state, and a powerful [hooking system](/docs/api/advanced/hooks) powered by [unjs/hookable](https://github.com/unjs/hookable)
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allowing different components to communicate with each other. You can think of it as **Builder Core**.
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This context is globally available to be used with [Nuxt Kit](/docs/guide/going-further/kit) composables.
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Therefore only one instance of Nuxt is allowed to run per process.
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To extend the Nuxt interface and hook into different stages of the build process, we can use [Nuxt Modules](/docs/guide/going-further/modules).
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For more details, check out [the source code](https://github.com/nuxt/nuxt/blob/main/packages/nuxt/src/core/nuxt.ts).
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## The NuxtApp Interface
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When rendering a page in the browser or on the server, a shared context will be created, referred to as `nuxtApp`.
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This context keeps vue instance, runtime hooks, and internal states like ssrContext and payload for hydration.
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You can think of it as **Runtime Core**.
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This context can be accessed using [`useNuxtApp()`](/docs/api/composables/use-nuxt-app) composable within Nuxt plugins and `<script setup>` and vue composables.
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Global usage is possible for the browser but not on the server, to avoid sharing context between users.
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Since [`useNuxtApp`](/docs/api/composables/use-nuxt-app) throws an exception if context is currently unavailable, if your composable does not always require `nuxtApp`, you can use [`tryUseNuxtApp`](/docs/api/composables/use-nuxt-app#tryusenuxtapp) instead, which will return `null` instead of throwing an exception.
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To extend the `nuxtApp` interface and hook into different stages or access contexts, we can use [Nuxt Plugins](/docs/guide/directory-structure/plugins).
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Check [Nuxt App](/docs/api/composables/use-nuxt-app) for more information about this interface.
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`nuxtApp` has the following properties:
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```js
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const nuxtApp = {
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vueApp, // the global Vue application: https://vuejs.org/api/application.html#application-api
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versions, // an object containing Nuxt and Vue versions
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// These let you call and add runtime NuxtApp hooks
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// https://github.com/nuxt/nuxt/blob/main/packages/nuxt/src/app/nuxt.ts#L18
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hooks,
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hook,
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callHook,
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// Only accessible on server-side
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ssrContext: {
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url,
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req,
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res,
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runtimeConfig,
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noSSR,
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},
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// This will be stringified and passed from server to client
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payload: {
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serverRendered: true,
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data: {},
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state: {}
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}
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provide: (name: string, value: any) => void
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}
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```
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For more details, check out [the source code](https://github.com/nuxt/nuxt/blob/main/packages/nuxt/src/app/nuxt.ts).
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## Runtime Context vs. Build Context
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Nuxt builds and bundles project using Node.js but also has a runtime side.
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While both areas can be extended, that runtime context is isolated from build-time. Therefore, they are not supposed to share state, code, or context other than runtime configuration!
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`nuxt.config` and [Nuxt Modules](/docs/guide/going-further/modules) can be used to extend the build context, and [Nuxt Plugins](/docs/guide/directory-structure/plugins) can be used to extend runtime.
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When building an application for production, `nuxi build` will generate a standalone build in the `.output` directory, independent of `nuxt.config` and [Nuxt modules](/docs/guide/going-further/modules).
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