Sometimes, we want to add an event bus with Vue.js 3.

In this article, we’ll look at how to add an event bus with Vue.js 3.

How to add an event bus with Vue.js 3?

To add an event bus with Vue.js 3, we can use the mitt package.

To install it, we run

npm install --save mitt

Then we use it by writing

import { createApp } from "vue";
import App from "./App.vue";
import mitt from "mitt";
const emitter = mitt();
const app = createApp(App);
app.config.globalProperties.emitter = emitter;
app.mount("#app");

in our app’s entry point file.

We make emitter available to all components with

app.config.globalProperties.emitter = emitter;

Then we use it by writing

<template>
  <header>
    <button @click="toggleSidebar">toggle</button>
  </header>
</template>

<script>
export default {
  data() {
    return {
      sidebarOpen: true,
    };
  },
  methods: {
    toggleSidebar() {
      this.sidebarOpen = !this.sidebarOpen;
      this.emitter.emit("toggle-sidebar", this.sidebarOpen);
    },
  },
};
</script>

We call this.emitter.emit to emit the toggle-sidebar event.

Then in another component, we write

<template>
  <aside class="sidebar" :class="{ 'sidebar--toggled': !isOpen }">...</aside>
</template>
<script>
export default {
  name: "sidebar",
  data() {
    return {
      isOpen: true,
    };
  },
  mounted() {
    this.emitter.on("toggle-sidebar", (isOpen) => {
      this.isOpen = isOpen;
    });
  },
};
</script>

to call this.emitter.on to listen to the toggle-siderbar event and get the value in the 2nd argument of emit from the isOpen parameter in the callback.

Conclusion

To add an event bus with Vue.js 3, we can use the mitt package.