This really shows up as an issue in unit testing, as it makes it tricky to ensure that each test is isolated from the last. With the old API, any global configuration we added (plugins, mixins, prototype properties etc) would permanently mutate global state. Next, we'll call the mount method on app and pass a CSS selector indicating our mount element, just like we did with the $mount instance method in Vue 2. We then call this method, passing our Vue instance definition object, and assign the return object to a variable app. Rather than using new Vue(), we now need to import the new createApp method. Straight off the bat, the way we bootstrap a new Vue app has changed. Now we'll run the dev server: $ npm run dev Once that's cloned and the NPM modules are installed, all we need to do is remove the boilerplate files and create a fresh main.js file so we can create our Vue 3 app from scratch. Rather than installing Vue 3 directly, let's clone the project vue-next-webpack-preview which will give us a minimal Webpack setup including Vue 3. Here's what the app looks like in it's opened and closed states so you can picture in your mind what we're working on: I chose this because it conveniently allows me to showcase a number of Vue 3 changes. At this stage, your component is still fully functional and nothing has been destroyed yet.Īn example of removing an event listener would look like this in the Options API.We're going to build a simple app with a modal window feature. beforeUnmount() and onBeforeUnmounted()īecause this is before the component starts to get torn down, this is the time to do most, if not all, of the clean up. This is the time for removing event listeners and things that could lead to memory leaks if not properly processed. The destruction hooks for a component are used in the process of removing a component and cleaning up all the loose ends. Watchers are good because they give the old value and the new value of the changed data.Īnother option is using computed values to change the state based on elements. These methods are useful, but for a lot of use cases we may want to consider using watchers to detect these data changes instead. Import from "vue" Ĭonsole.log("updated() val: " + val.value)
#VUE 3 CODE#
Take the following code block for example: Since the created hook is the thing that initializes all of the reactive data and events, beforeCreate does not have access to any of a component’s reactive data and events. Creation Hooks – The Start of the VueJS LifecycleĬreation hooks are the very first thing that runs in your program. Let’s take a deeper dive at each lifecycle hook and look at how they’re used, what kind of code we can write in each one, and the differences between them in the Options API and Composition API. How to use them in both the Options API and the Composition API This handy Vue 2 to Vue 3 lifecycle mapping is straight from the Vue 3 Composition API docs and I think it’s one of the most useful ways to see exactly how things are going to be changing and how we can use them. Updating Vue 2 Code to Vue 3 Lifecycle Hooks It might look something like this.Ĭonsole.log("mounted in the composition api!") We don’t need to import anything, we can just invoke the method and write the code for that lifecycle hook.įor example, let’s say we wanted to access our mounted() and our updated() lifecycle hooks. With the Options API, our lifecycle hooks are exposed as options on our Vue instance. Using our Vue Lifecycle Hooks in the Options API Updates - runs when reactive data is modifiedĭestruction - runs right before your element is destroyed. There are four main events (8 main hooks) that you can utilize in your Vue app.Ĭreation - runs on your component’s creation This should give a high level overview of what’s going on before we can dive down into the details.Įssentially, each main Vue lifecycle event is separated into two hooks that are called right before that event and then right after. Let’s go! What are the Vue Lifecycle Hooksįirst, let’s look at a diagram of the Vue 3 lifecycle hooks in both the Options API and Composition API.
#VUE 3 HOW TO#
However, the way we access these hooks is a little bit different when we decide to use the Composition API – which is especially useful in larger Vue projects.īy the end of this article, you’ll know how to use lifecycle hooks in both the Options API and Composition API and be on your way to writing better code. This is because Vue 3 is designed to be compatible with prior releases of Vue. If our project uses the Options API, we don’t have to change any of the code for our Vue lifecycle hooks. Lifecycle hooks in both Vue 2 and Vue 3 work very similarly – we still have access to the same hooks and we still want to use them for the same use cases.
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