How to use onBeforeMount in Vue
Łukasz Holeczek
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Executing code right before a component is mounted to the DOM is essential for last-minute setup and preparation tasks in Vue applications.
As the creator of CoreUI, a widely used open-source UI library, and with over 11 years of experience in software development including Vue.js since 2014, I’ve implemented countless components that require pre-mounting configuration.
The most effective approach is using the onBeforeMount lifecycle hook in Vue 3’s Composition API, which provides the perfect timing for final preparations before DOM creation.
This hook is ideal for tasks that need to happen after reactive setup but before the component becomes visible.
Use onBeforeMount in the Composition API to execute code immediately before the component is mounted to the DOM.
import { onBeforeMount, ref } from 'vue'
export default {
setup() {
const isReady = ref(false)
onBeforeMount(() => {
console.log('Component is about to mount')
isReady.value = true
})
return { isReady }
}
}
The onBeforeMount hook is called right before the component is mounted to the DOM. At this point, the component has finished setting up its reactive state and computed properties, but the DOM has not yet been created. This timing makes it perfect for final configuration tasks, logging, or setting up external libraries that need to be ready before the component renders but don’t require DOM access.
Best Practice Note:
This is the approach we use in CoreUI Vue components for initializing third-party libraries and performing final setup tasks. Unlike onMounted, this hook doesn’t have access to DOM elements, so use it for logic that prepares the component rather than manipulates the rendered output.
