Explain Stores (Vuex) Like I'm Five

A Vue application is a tree of components. Each component has 0 or 1 parents and 0 or more children.

In Vue, you usually send information from one component to another in a straight line, up or down.

You use props to pass data down the component tree, and events to pass it back up.

This isn't so great if you've got a really big tree. Passing hundreds of notes back and forth gets to be a real pain.

Another option is to put all your data in JavaScript singletons, like a bunch of cardboard boxes that your application can pass around to whoever needs it.

This isn't a bad solution, necessarily, but what if it could be better?

Vuex is like a train where each car has the same shape.

The first train car, the locomotive, has all the data your components need to share. Whenever you want to change that data, you commit an action or a mutation. This is like adding another car to the train. It has the same shape as the locomotive, just different data inside.

Why is this better than cardboard boxes? Because if something goes wrong while you're watching, you can pause the train or put it in reverse. You can inspect two cars and see what's different between them. You can debug the entire train instead of just one car.

Vuex also works really well with the Vue Devtools, an official browser extension, so you can easily watch what actions/mutations are happening and how the data is changing.

So Vuex makes it super easy to organize data, share it between components, and observe when it changes. How do you use it?

A Vuex store is a blueprint for one of those train cars. It looks like this:

const dataStore = {
  state: {
    dataToShare: 0
  },
  mutations: {
    'CHANGE_DATA': function(newData) {
      this.dataToShare = newData;
    }
  }
}

export default dataStore;

And you can register it like this:

import Vuex from 'vuex';
import dataStore from './dataStore';

new Vuex.store({
  modules: {
    dataStore: dataStore
  }
});

Then in a Vue component, in any method or lifecycle hook, you can do this:

this.$store.commit('CHANGE_DATA', 1);

Voila! Now dataToShare is equal to 1. If you're debugging and need to rewind it to 0, you can do so using the Vue Devtools.

To access dataToShare in any component, you can do this:

const componentData = this.$store.state.dataStore.dataToShare

Usually you would do this in a computed method, so that every time dataToShare changes, your component gets updated. This is another advantage of Vuex: it hooks into Vue's reactivity system, so when data updates, your application updates too.

That's pretty much it! Any questions?