vuex/docs/guide/migrating-to-4-0-from-3-x.md

Migrating to 4.0 from 3.x

Almost all Vuex 4 APIs have remained unchanged from Vuex 3. However, there are still a few breaking changes that you must fix.

• Breaking Changes
  • Installation process
  • TypeScript support
  • Bundles are now aligned with Vue 3
  • "createLogger" function is exported from the core module
• New Features
  • New "useStore" composition function

Breaking Changes

Installation process

To align with the new Vue 3 initialization process, the installation process of Vuex has changed. To create a new store, users are now encouraged to use the newly introduced createStore function.

import { createStore } from 'vuex'

export const store = createStore({
  state () {
    return {
      count: 1
    }
  }
})

To install Vuex to a Vue instance, pass the store instead of Vuex.

import { createApp } from 'vue'
import { store } from './store'
import App from './App.vue'

const app = createApp(App)

app.use(store)

app.mount('#app')

:::tip NOTE Whilst this is not technically a breaking change, you may still use the new Store(...) syntax, we recommend this approach to align with Vue 3 and Vue Router Next. :::

TypeScript support

Vuex 4 removes its global typings for this.$store within a Vue component to solve issue #994. When used with TypeScript, you must declare your own module augmentation.

Place the following code in your project to allow this.$store to be typed correctly:

// vuex-shim.d.ts

import { ComponentCustomProperties } from 'vue'
import { Store } from 'vuex'

declare module 'vue' {
  // Declare your own store states.
  interface State {
    count: number
  }

  interface ComponentCustomProperties {
    $store: Store<State>
  }
}

You can learn more in the TypeScript Support section.

Bundles are now aligned with Vue 3

The following bundles are generated to align with Vue 3 bundles:

• vuex.global(.prod).js
  • For direct use with <script src="..."> in the browser. Exposes the Vuex global.
  • Global build is built as IIFE, and not UMD, and is only meant for direct use with <script src="...">.
  • Contains hard-coded prod/dev branches and the prod build is pre-minified. Use the .prod.js files for production.
• vuex.esm-browser(.prod).js
  • For use with native ES module imports (including module supporting browsers via <script type="module">.
• vuex.esm-bundler.js
  • For use with bundlers such as webpack, rollup and parcel.
  • Leaves prod/dev branches with process.env.NODE_ENV guards (must be replaced by bundler).
  • Does not ship minified builds (to be done together with the rest of the code after bundling).
• vuex.cjs.js
  • For use in Node.js server-side rendering with require().

createLogger function is exported from the core module

In Vuex 3, createLogger function was exported from vuex/dist/logger but it's now included in the core package. The function should be imported directly from the vuex package.

import { createLogger } from 'vuex'

New Features

New useStore composition function

Vuex 4 introduces a new API to interact with the store in Composition API. You can use the useStore composition function to retrieve the store within the component setup hook.

import { useStore } from 'vuex'

export default {
  setup () {
    const store = useStore()
  }
}

You can learn more in the Composition API section.