Application API#

createApp()#

Creates an application instance.

• Type

ts function createApp(rootComponent: Component, rootProps?: object): App

• Details

The first argument is the root component. The second optional argument is the props to be passed to the root component.

• Example

With inline root component:

```js import { createApp } from 'vue'

const app = createApp({ / root component options / }) ```

With imported component:

```js import { createApp } from 'vue' import App from './App.vue'

const app = createApp(App) ```

• See also Guide - Creating a Vue Application

createSSRApp()#

Creates an application instance in SSR Hydration mode. Usage is exactly the same as createApp().

app.mount()#

Mounts the application instance in a container element.

• Type

ts interface App { mount(rootContainer: Element | string): ComponentPublicInstance }

• Details

The argument can either be an actual DOM element or a CSS selector (the first matched element will be used). Returns the root component instance.

If the component has a template or a render function defined, it will replace any existing DOM nodes inside the container. Otherwise, if the runtime compiler is available, the innerHTML of the container will be used as the template.

In SSR hydration mode, it will hydrate the existing DOM nodes inside the container. If there are mismatches, the existing DOM nodes will be morphed to match the expected output.

For each app instance, mount() can only be called once.

• Example

```js import { createApp } from 'vue' const app = createApp(/ ... /)

app.mount('#app') ```

Can also mount to an actual DOM element:

js app.mount(document.body.firstChild)

app.unmount()#

Unmounts a mounted application instance, triggering the unmount lifecycle hooks for all components in the application's component tree.

• Type

ts interface App { unmount(): void }

app.onUnmount() <sup>#</sup>

Registers a callback to be called when the app is unmounted.

• Type

ts interface App { onUnmount(callback: () => any): void }

app.component()#

Registers a global component if passing both a name string and a component definition, or retrieves an already registered one if only the name is passed.

• Type

ts interface App { component(name: string): Component | undefined component(name: string, component: Component): this }

• Example

```js import { createApp } from 'vue'

const app = createApp({})

// register an options object app.component('MyComponent', { / ... / })

// retrieve a registered component const MyComponent = app.component('MyComponent') ```

• See also Component Registration

app.directive()#

Registers a global custom directive if passing both a name string and a directive definition, or retrieves an already registered one if only the name is passed.

• Type

ts interface App { directive(name: string): Directive | undefined directive(name: string, directive: Directive): this }

• Example

```js import { createApp } from 'vue'

const app = createApp({ / ... / })

// register (object directive) app.directive('myDirective', { / custom directive hooks / })

// register (function directive shorthand) app.directive('myDirective', () => { / ... / })

// retrieve a registered directive const myDirective = app.directive('myDirective') ```

• See also Custom Directives

app.use()#

Installs a plugin.

• Type

ts interface App { use(plugin: Plugin, ...options: any[]): this }

• Details

Expects the plugin as the first argument, and optional plugin options as the second argument.

The plugin can either be an object with an install() method, or just a function that will be used as the install() method. The options (second argument of app.use()) will be passed along to the plugin's install() method.

When app.use() is called on the same plugin multiple times, the plugin will be installed only once.

• Example

```js import { createApp } from 'vue' import MyPlugin from './plugins/MyPlugin'

const app = createApp({ / ... / })

app.use(MyPlugin) ```

• See also Plugins

app.mixin()#

Applies a global mixin (scoped to the application). A global mixin applies its included options to every component instance in the application.

:::warning Not Recommended Mixins are supported in Vue 3 mainly for backwards compatibility, due to their widespread use in ecosystem libraries. Use of mixins, especially global mixins, should be avoided in application code.

For logic reuse, prefer Composables instead. :::

• Type

ts interface App { mixin(mixin: ComponentOptions): this }

app.provide()#

Provide a value that can be injected in all descendant components within the application.

• Type

ts interface App { provide<T>(key: InjectionKey<T> | symbol | string, value: T): this }

• Details

Expects the injection key as the first argument, and the provided value as the second. Returns the application instance itself.

• Example

```js import { createApp } from 'vue'

const app = createApp(/ ... /)

app.provide('message', 'hello') ```

Inside a component in the application:

• See also
• Provide / Inject
• App-level Provide
• app.runWithContext()

app.runWithContext()#

• Only supported in 3.3+

Execute a callback with the current app as injection context.

• Type

ts interface App { runWithContext<T>(fn: () => T): T }

• Details

Expects a callback function and runs the callback immediately. During the synchronous call of the callback, inject() calls are able to look up injections from the values provided by the current app, even when there is no current active component instance. The return value of the callback will also be returned.

• Example

```js import { inject } from 'vue'

app.provide('id', 1)

const injected = app.runWithContext(() => { return inject('id') })

console.log(injected) // 1 ```

app.version#

Provides the version of Vue that the application was created with. This is useful inside plugins, where you might need conditional logic based on different Vue versions.

• Type

ts interface App { version: string }

• Example

Performing a version check inside a plugin:

js export default { install(app) { const version = Number(app.version.split('.')[0]) if (version < 3) { console.warn('This plugin requires Vue 3') } } }

• See also Global API - version

app.config#

Every application instance exposes a config object that contains the configuration settings for that application. You can modify its properties (documented below) before mounting your application.

import { createApp } from 'vue'

const app = createApp(/* ... */)

console.log(app.config)

app.config.errorHandler#

Assign a global handler for uncaught errors propagating from within the application.

• Type

ts interface AppConfig { errorHandler?: ( err: unknown, instance: ComponentPublicInstance | null, // `info` is a Vue-specific error info, // e.g. which lifecycle hook the error was thrown in info: string ) => void }

• Details

The error handler receives three arguments: the error, the component instance that triggered the error, and an information string specifying the error source type.

It can capture errors from the following sources:

• Component renders
• Event handlers
• Lifecycle hooks
• setup() function
• Watchers
• Custom directive hooks
• Transition hooks

:::tip In production, the 3rd argument (info) will be a shortened code instead of the full information string. You can find the code to string mapping in the Production Error Code Reference. :::

• Example

js app.config.errorHandler = (err, instance, info) => { // handle error, e.g. report to a service }

• Default

The default error handler will re-throw errors during development and log errors during production. You can configure this using the throwUnhandledErrorInProduction property.

app.config.warnHandler#

Assign a custom handler for runtime warnings from Vue.

• Type

ts interface AppConfig { warnHandler?: ( msg: string, instance: ComponentPublicInstance | null, trace: string ) => void }

• Details

The warning handler receives the warning message as the first argument, the source component instance as the second argument, and a component trace string as the third.

It can be used to filter out specific warnings to reduce console verbosity. All Vue warnings should be addressed during development, so this is only recommended during debug sessions to focus on specific warnings among many, and should be removed once the debugging is done.

:::tip Warnings only work during development, so this config is ignored in production mode. :::

• Example

js app.config.warnHandler = (msg, instance, trace) => { // `trace` is the component hierarchy trace }

app.config.performance#

Set this to true to enable component init, compile, render and patch performance tracing in the browser devtool performance/timeline panel. Only works in development mode and in browsers that support the performance.mark API.

• Type: boolean

• See also Guide - Performance

app.config.compilerOptions#

Configure runtime compiler options. Values set on this object will be passed to the in-browser template compiler and affect every component in the configured app. Note you can also override these options on a per-component basis using the compilerOptions option.

::: warning Important This config option is only respected when using the full build (i.e. the standalone vue.js that can compile templates in the browser). If you are using the runtime-only build with a build setup, compiler options must be passed to @vue/compiler-dom via build tool configurations instead.

• For vue-loader: pass via the compilerOptions loader option. Also see how to configure it in vue-cli.

• For vite: pass via @vitejs/plugin-vue options. :::

app.config.compilerOptions.isCustomElement#

Specifies a check method to recognize native custom elements.

• Type: (tag: string) => boolean

• Details

Should return true if the tag should be treated as a native custom element. For a matched tag, Vue will render it as a native element instead of attempting to resolve it as a Vue component.

Native HTML and SVG tags don't need to be matched in this function - Vue's parser recognizes them automatically.

• Example

js // treat all tags starting with 'ion-' as custom elements app.config.compilerOptions.isCustomElement = (tag) => { return tag.startsWith('ion-') }

• See also Vue and Web Components

app.config.compilerOptions.whitespace#

Adjusts template whitespace handling behavior.

• Type: 'condense' | 'preserve'

• Default: 'condense'

• Details

Vue removes / condenses whitespace characters in templates to produce more efficient compiled output. The default strategy is "condense", with the following behavior:

1. Leading / ending whitespace characters inside an element are condensed into a single space.
2. Whitespace characters between elements that contain newlines are removed.
3. Consecutive whitespace characters in text nodes are condensed into a single space.

Setting this option to 'preserve' will disable (2) and (3).

• Example

js app.config.compilerOptions.whitespace = 'preserve'

app.config.compilerOptions.delimiters#

Adjusts the delimiters used for text interpolation within the template.

• Type: [string, string]

• Default: {{ "['\u007b\u007b', '\u007d\u007d']" }}

• Details

This is typically used to avoid conflicting with server-side frameworks that also use mustache syntax.

• Example

js // Delimiters changed to ES6 template string style app.config.compilerOptions.delimiters = ['${', '}']

app.config.compilerOptions.comments#

Adjusts treatment of HTML comments in templates.

• Type: boolean

• Default: false

• Details

By default, Vue will remove the comments in production. Setting this option to true will force Vue to preserve comments even in production. Comments are always preserved during development. This option is typically used when Vue is used with other libraries that rely on HTML comments.

• Example

js app.config.compilerOptions.comments = true

app.config.globalProperties#

An object that can be used to register global properties that can be accessed on any component instance inside the application.

• Type

ts interface AppConfig { globalProperties: Record<string, any> }

• Details

This is a replacement of Vue 2's Vue.prototype which is no longer present in Vue 3. As with anything global, this should be used sparingly.

If a global property conflicts with a component’s own property, the component's own property will have higher priority.

• Usage

js app.config.globalProperties.msg = 'hello'

This makes msg available inside any component template in the application, and also on this of any component instance:

js export default { mounted() { console.log(this.msg) // 'hello' } }

• See also Guide - Augmenting Global Properties

app.config.optionMergeStrategies#

An object for defining merging strategies for custom component options.

• Type

```ts interface AppConfig { optionMergeStrategies: Record }

type OptionMergeFunction = (to: unknown, from: unknown) => any ```

• Details

Some plugins / libraries add support for custom component options (by injecting global mixins). These options may require special merging logic when the same option needs to be "merged" from multiple sources (e.g. mixins or component inheritance).

A merge strategy function can be registered for a custom option by assigning it on the app.config.optionMergeStrategies object using the option's name as the key.

The merge strategy function receives the value of that option defined on the parent and child instances as the first and second arguments, respectively.

• Example

```js const app = createApp({ // option from self msg: 'Vue', // option from a mixin mixins: [ { msg: 'Hello ' } ], mounted() { // merged options exposed on this.$options console.log(this.$options.msg) } })

// define a custom merge strategy for msg app.config.optionMergeStrategies.msg = (parent, child) => { return (parent || '') + (child || '') }

app.mount('#app') // logs 'Hello Vue' ```

• See also Component Instance - $options

app.config.idPrefix <sup>#</sup>

Configure a prefix for all IDs generated via useId() inside this application.

• Type: string

• Default: undefined

• Example

js app.config.idPrefix = 'myApp'

js // in a component: const id1 = useId() // 'myApp:0' const id2 = useId() // 'myApp:1'

app.config.throwUnhandledErrorInProduction <sup>#</sup>

Force unhandled errors to be thrown in production mode.

• Type: boolean

• Default: false

• Details

By default, errors thrown inside a Vue application but not explicitly handled have different behavior between development and production modes:

• In development, the error is thrown and can possibly crash the application. This is to make the error more prominent so that it can be noticed and fixed during development.

• In production, the error will only be logged to the console to minimize the impact to end users. However, this may prevent errors that only happen in production from being caught by error monitoring services.

By setting app.config.throwUnhandledErrorInProduction to true, unhandled errors will be thrown even in production mode.