Where can the state be stored in Vue? When is it better to use Pinia/Vuex, and when provide/inject?

In Vue, state can be stored in several ways:

1. Local component state — data inside the data() of a specific component.
2. Provide/Inject — a mechanism for passing data from parent to descendants without props, suitable for limited hierarchical data sharing.
3. Global state via Pinia or Vuex — a centralized store for the entire application.

When to use:

• Provide/Inject

  • When you need to pass data or functions deep down the component tree without passing props.
  • For small, local dependencies.
  • Not suitable for reactive global state, as tracking changes is difficult.

• Pinia/Vuex

  • For managing the application's global state.
  • When multiple components need access to the same data and should react to its changes.
  • For complex logic, asynchronous actions, and state mutations.

Example of using Pinia:

import { defineStore } from 'pinia'

export const useCounterStore = defineStore('counter', {
  state: () => ({ count: 0 }),
  actions: {
    increment() {
      this.count++
    }
  }
})

Summary:

• For simple cases and passing data down the tree — provide/inject.
• For complex, reactive, global state — Pinia or Vuex.