Persisting store state in Vue

Introduction

Persisting store state means saving your app's data so it stays even after you refresh the page or close the browser. This helps users keep their progress or settings without losing them.

You want to save user preferences like theme or language so they don't reset on reload.

You have a shopping cart in an online store and want it to remember items after closing the tab.

You want to keep form data saved if the user accidentally refreshes the page.

You want to save login status so users don't have to sign in every time they visit.

You want to keep game progress or scores saved between sessions.

Syntax

Vue

import { createStore } from 'vuex'
import createPersistedState from 'vuex-persistedstate'

const store = createStore({
  state() {
    return {
      count: 0
    }
  },
  mutations: {
    increment(state) {
      state.count++
    }
  },
  plugins: [createPersistedState()]
})

export default store

The vuex-persistedstate plugin automatically saves and loads the store state to localStorage.

You add it in the plugins array when creating the store.

Examples

This enables default localStorage persistence for the whole store.

Vue

plugins: [createPersistedState()]

This saves the store state in sessionStorage instead of localStorage, so data clears when the tab closes.

Vue

plugins: [createPersistedState({ storage: window.sessionStorage })]

This saves only the user and settings parts of the store state.

Vue

plugins: [createPersistedState({ paths: ['user', 'settings'] })]

Sample Program

This Vue app uses Vuex with the persisted state plugin. When you click the button, the count increases and is saved. Refreshing the page keeps the count value.

Vue

import { createApp } from 'vue'
import { createStore } from 'vuex'
import createPersistedState from 'vuex-persistedstate'

const store = createStore({
  state() {
    return {
      count: 0
    }
  },
  mutations: {
    increment(state) {
      state.count++
    }
  },
  plugins: [createPersistedState()]
})

const app = createApp({
  computed: {
    count() {
      return store.state.count
    }
  },
  methods: {
    increment() {
      store.commit('increment')
    }
  },
  template: `
    <div>
      <p>Count: {{ count }}</p>
      <button @click="increment">Increment</button>
      <p>Refresh the page and the count stays the same.</p>
    </div>
  `
})

app.use(store)
app.mount('#app')

Important Notes

Persisted state usually uses localStorage, which keeps data even after closing the browser.

Be careful not to store sensitive data in localStorage because it is accessible by JavaScript.

You can customize which parts of the store to save using the paths option.

Summary

Persisting store state saves your app data so it stays after refresh or closing the browser.

Use the vuex-persistedstate plugin to easily add this feature.

You can choose where and what to save for better control and security.

Practice

1. What is the main purpose of persisting store state in a Vue application?

easy

A. To speed up the app by caching components

B. To keep the app data saved even after refreshing or closing the browser

C. To automatically update the UI without user input

D. To prevent users from logging out

Solution

1. Step 1: Understand what persisting store state means

   Persisting store state means saving the app's data so it does not disappear when the page reloads or the browser closes.

2. Step 2: Identify the main benefit

   This helps keep user data or app settings intact, improving user experience.

3. Final Answer:

   To keep the app data saved even after refreshing or closing the browser -> Option B

4. Quick Check:

   Persisting state = saving data after refresh [OK]

Hint: Persisting means saving data beyond page reloads [OK]

Common Mistakes:

• Confusing persisting with caching UI components
• Thinking it automatically updates UI without user action
• Believing it prevents user logout directly

2. Which of the following is the correct way to add the vuex-persistedstate plugin to a Vuex store?

easy

A. import createPersistedState from 'vuex-persistedstate';

const store = createStore({
plugins: createPersistedState
});

B. import createPersistedState from 'vuex-persistedstate';

const store = createStore({
persist: createPersistedState()
});

C. import createPersistedState from 'vuex-persistedstate';

const store = createStore({
plugins: [createPersistedState()]
});

D. import createPersistedState from 'vuex-persistedstate';

const store = createStore({
plugins: [createPersistedState]
});

Solution

1. Step 1: Recall the plugin usage syntax

   The vuex-persistedstate plugin is imported as a function and added inside the plugins array when creating the store.

2. Step 2: Check the correct syntax

   import createPersistedState from 'vuex-persistedstate'; const store = createStore({ plugins: [createPersistedState()] }); correctly imports and calls createPersistedState() inside the plugins array.

3. Final Answer:

   import createPersistedState from 'vuex-persistedstate'; const store = createStore({ plugins: [createPersistedState()] }); -> Option C

4. Quick Check:

   Plugin added as function in plugins array [OK]

Hint: Plugins go inside plugins array, called as functions [OK]

Common Mistakes:

• Putting plugin directly as object property instead of in plugins array
• Not calling the plugin function with ()
• Passing plugin without wrapping in array

3. Given this Vuex store setup with vuex-persistedstate:

import { createStore } from 'vuex';
import createPersistedState from 'vuex-persistedstate';

const store = createStore({
  state() {
    return { count: 0 };
  },
  mutations: {
    increment(state) {
      state.count++;
    }
  },
  plugins: [createPersistedState()]
});

store.commit('increment');

// After page reload, what is the value of store.state.count?

medium

A. 1

B. Error

C. undefined

D. 0

Solution

1. Step 1: Understand what happens on commit

   The mutation increment increases count from 0 to 1.

2. Step 2: Effect of vuex-persistedstate plugin

   This plugin saves the state to localStorage, so after page reload, the state is restored with count still 1.

3. Final Answer:

   1 -> Option A

4. Quick Check:

   Persisted state restores count = 1 after reload [OK]

Hint: Persisted state keeps mutations after reload [OK]

Common Mistakes:

• Assuming state resets to initial value after reload
• Thinking plugin does not save mutations
• Confusing undefined or error with normal behavior

4. You added vuex-persistedstate to your Vuex store but the state is not saved after refresh. Which of these is the most likely cause?

medium

A. You forgot to call the plugin function inside the plugins array

B. You did not import Vuex correctly

C. You used mutations instead of actions

D. You did not define the initial state

Solution

1. Step 1: Check plugin usage

   If the plugin is added without calling it as a function (missing parentheses), it won't activate and save state.

2. Step 2: Verify other options

   Importing Vuex correctly, using mutations, and defining initial state are unrelated to plugin activation.

3. Final Answer:

   You forgot to call the plugin function inside the plugins array -> Option A

4. Quick Check:

   Plugin must be called as function to work [OK]

Hint: Always call plugin with () inside plugins array [OK]

Common Mistakes:

• Adding plugin without parentheses
• Blaming mutations or initial state for persistence issues
• Ignoring plugin import errors

5. You want to persist only the user part of your Vuex state and store it in sessionStorage instead of localStorage. Which is the correct way to configure vuex-persistedstate?

hard

A. plugins: [createPersistedState({ only: ['user'], storage: window.sessionStorage })]

B. plugins: [createPersistedState({ paths: ['user'], storage: 'sessionStorage' })]

C. plugins: [createPersistedState({ keys: ['user'], storage: sessionStorage })]

D. plugins: [createPersistedState({ paths: ['user'], storage: window.sessionStorage })]

Solution

1. Step 1: Use the correct option to select parts of state

   The paths option specifies which parts of the state to save, so paths: ['user'] is correct.

2. Step 2: Set storage to sessionStorage correctly

   The storage option expects the storage object, so window.sessionStorage is correct.

3. Final Answer:

   plugins: [createPersistedState({ paths: ['user'], storage: window.sessionStorage })] -> Option D

4. Quick Check:

   Use paths and window.sessionStorage for selective session storage [OK]

Hint: Use paths array and window.sessionStorage for selective session saving [OK]

Common Mistakes:

• Using string 'sessionStorage' instead of window.sessionStorage object
• Using wrong option names like only or keys
• Not specifying paths to limit saved state