Vue Js Emit

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Binding Native Events to Components

You could emit your event all the way back up the chain (although this can start to get quite messy if you're having to emit any further than grandchild to grandparent). You could use a dedicated state management system such as Vuex, which can help to simplify the process of emitting from deeply nested components. I'd certainly recommend this route and we'll be definitely look to cover this in a future post!

Why $emit()?

Or you could use something known as a Global Event Bus. You can think of this as implementing your own simplified version of a state management system such as Vuex. However, it is worth noting that Vue's core team generally advises against the use of Global Event Buses in favor of something more robust, such as Vuex.

Pro Tips for emitting custom events

We won't go into the reasons for this any further here, but it's certainly worth researching further if this is something you are considering in your app. this.$emit dispatches an event to its parent component.

this.$parent gives you a reference to the parent component.

  • this.$root gives you a reference to the root component.
  • this.$parent.$emit will make the parent dispatch the event to its parent.
  • this.$root.$emit will make the root dispatch the event to itself.
  • You’re browsing the documentation for v2.x and earlier.
  • For v3.x, click here. This page assumes you’ve already read the Components Basics.
  • Read that first if you are new to components.

Customizing Component v-model

Unlike components and props, event names don’t provide any automatic case transformation. Instead, the name of an emitted event must exactly match the name used to listen to that event.

Emitting Events in the Options API with this.$emit

For example, if emitting a camelCased event name:. Listening to the kebab-cased version will have no effect:. Unlike components and props, event names will never be used as variable or property names in JavaScript, so there’s no reason to use camelCase or PascalCase.

Additionally, v-on event listeners inside DOM templates will be automatically transformed to lowercase (due to HTML’s case-insensitivity), so v-on:myEvent would become v-on:myevent – making myEvent impossible to listen to.

For these reasons, we recommend you always use kebab-case for event names. By default, v-model on a component uses value as the prop and input as the event, but some input types such as checkboxes and radio buttons may want to use the value attribute for a different purpose.

Using the model option can avoid a conflict in such cases:. Now when using v-model on this component:.

the value of lovingVue will be passed to the checked prop.

How does Vue Emit Work?

The lovingVue property will then be updated when emits a change event with a new value. Note that you still have to declare the checked prop in the component’s props option.

Event Names

There may be times when you want to listen directly to a native event on the root element of a component. In these cases, you can use the .native modifier for v-on:. This can be useful sometimes, but it’s not a good idea when you’re trying to listen on a very specific element, like an .

For example, the component above might refactor so that the root element is actually a

There would be no errors, but the onFocus handler wouldn’t be called when we expected it to. To solve this problem, Vue provides a $listeners property containing an object of listeners being used on the component.

Final Thoughts

Using the $listeners property, you can forward all event listeners on the component to a specific child element with v-on="$listeners".

For elements like , that you also want to work with v-model, it’s often useful to create a new computed property for listeners, like inputListeners below:.

Now the component is a fully transparent wrapper, meaning it can be used exactly like a normal element: all the same attributes and listeners will work, without the .native modifier.

In some cases, we may need “two-way binding” for a prop. Unfortunately, true two-way binding can create maintenance issues, because child components can mutate the parent without the source of that mutation being obvious in both the parent and the child.

That’s why instead, we recommend emitting events in the pattern of update:myPropName. For example, in a hypothetical component with a title prop, we could communicate the intent of assigning a new value with:. Then the parent can listen to that event and update a local data property, if it wants to.

For convenience, we offer a shorthand for this pattern with the .sync modifier:. Note that v-bind with the .sync modifier does not work with expressions (e.g. v-bind:title.sync=”doc.title + ‘!’” is invalid). Instead, you must only provide the name of the property you want to bind, similar to v-model.

The .sync modifier can also be used with v-bind when using an object to set multiple props at once:. This passes each property in the doc object (e.g. title) as an individual prop, then adds v-on update listeners for each one.

Using v-bind.sync with a literal object, such as in v-bind.sync=”{ title: doc.title }”, will not work, because there are too many edge cases to consider in parsing a complex expression like this.

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Vue components have a $emit() function that allows you to pass custom events up the component tree. All Vue instances have a $emit() function, including both top-level apps andindividual components.

Generally, you use $emit() to notify the parent component that something changed.

.sync Modifier

For example, suppose you have a component input-name that takes a prop called name. This component exposes an input form asking the user for their name, and an 'Update' button that updates the name. The way to do this is for input-name to $emit() an event called 'update' when the user clicks the 'Update' button, with the new name.