Vue Events are the building blocks of inter-component communication in Vue.js, enabling seamless coordination between different parts of your application.
Whether you’re a beginner or an experienced Vue developer, this guide will provide you with a solid foundation in Vue events.
With practical examples and step-by-step explanations, you’ll gain the confidence to implement event-driven functionality and create dynamic Vue applications. Let’s dive in!
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Learn more by reading my longer article about How To Use Vue 3 Emit And Vue 3 Emit Composition API
Vue Events
Vue Events can be seen as a signal or message that a component emits to inform other components about a specific action or change in state.
What Are Events In Vue?
In Vue, events serve as a mechanism for inter-component communication. They enable components to interact by emitting and listening to events.
Essentially, an event can be seen as a signal or message that a component emits to inform other components about a specific action or change in state.
By emitting events, components can notify others, allowing them to execute custom logic or update their properties accordingly.
The beauty of events lies in their decoupled nature, as they enable modular and reusable component development without tight coupling.
Components can communicate and collaborate by emitting and listening to events without needing detailed knowledge about each other’s internal workings.
This separation promotes code reusability and maintainability.
Vue Events Emit
Vue Events Emit: To emit an event in Vue, you utilize the $emit method provided by the component instance.
The $emit method requires two arguments: the name of the event to emit and an optional payload, which represents the data to be passed along with the event.
Typically, the event name is a descriptive string that conveys the purpose or action associated with the event.
Here’s an example that demonstrates emitting an event in Vue:
In this example, when the button is clicked, the emitEvent method is triggered.
Within this method, this.$emit(‘custom-event’, ‘Some data’) emits a custom event named ‘custom-event’ and passes the string ‘Some data’ as the payload.
Consequently, other components can capture and respond to this event.
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Vue Events Mounted
Vue Events Mounted: In Vue, the mounted lifecycle hook plays a significant role in executing specific tasks when a component is inserted into the DOM and becomes “mounted.”
This hook acts as a convenient location for performing initialization operations, such as setting up event listeners.
Consider the following example, which illustrates using the mounted hook to listen to an event:
In this example, the parent component (ParentComponent) includes the ChildComponent and listens for the ‘custom-event’.
Within the mounted hook, this.$on(‘custom-event’, this.handleEvent) registers the handleEvent method as the event listener for the ‘custom-event’.
When the child component emits the event, the parent component’s handleEvent method will be invoked, receiving the payload passed with the event.
Vue Events List
Vue Events List: To begin, let’s imagine a scenario where we have a parent component called “App” and a child component called “EventList.”
The goal is to display a list of events in the child component and emit an event when a specific event is clicked.
First, we need to define the event list in the parent component, “App.”
We can create an array of event objects, each containing properties such as the event name, description, and date. For instance:
Next, we pass the event list as a prop to the child component, “EventList.” In the child component, we can iterate over the events array and display the event information using a loop:
In the child component, we use the v-for directive to iterate over each event in the events array and display its name.
We also bind the @click event to the emitEvent method, passing the event object as a parameter.
Inside the emitEvent method, we use this.$emit to emit a custom event called “event-clicked” along with the event object as data.
Finally, in the parent component, “App,” we can listen for the “event-clicked” event and handle it accordingly:
In the parent component, we import and register the child component, “EventList.”
We pass the events array as a prop to the “EventList” component, and we use the @event-clicked event listener to call the handleEventClicked method when an event is clicked.
Inside the handleEventClicked method, we can perform any desired actions, such as displaying additional information or updating the parent component’s state.
Vue Events Between Components
Vue Events Between Components: Vue events are particularly useful for establishing communication between components.
By emitting events from one component and listening to them in another, components can exchange data, trigger actions, and keep each other informed about relevant changes.
Consider the following example to illustrate how events facilitate communication between parent and child components:
In this example, the parent component (ParentComponent) includes the child component (ChildComponent) and listens for the ‘custom-event’.
When the button in the child component is clicked, it emits the ‘custom-event’ with the payload ‘Some data’.
The parent component’s handleEvent method captures the event and logs the received payload to the console.
By utilizing events, components can effectively communicate and coordinate their actions, enabling the development of flexible and modular applications.
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Vue Events Change
Vue Events Change: Vue events can also be leveraged to track changes in component properties or states.
By emitting events whenever a change occurs, components can notify others and trigger relevant actions or updates.
Consider the following example, which demonstrates using events to track changes in a component:
In this example, the child component contains an input field bound to the name data property using v-model.
Whenever the input value changes, the @input event is triggered, invoking the emitChange method.
The emitChange method emits the ‘name-change’ event and passes the updated name value as the payload.
Other components can listen to this event and perform actions based on the changed name value.
Vue Event
Vue Event Handler
Vue Event Handler: Event handler is a method or function that is executed in response to a specific event being triggered.
They’re are defined within the methods object of a Vue component.
To attach an event handler to an element, you can use the v-on directive followed by the event name and the method reference.
Here’s an example of a Vue event handler:
In the example above, the handleClick method is called when the button is clicked. The method logs a message to the console.
You can perform various actions inside the event handler, such as updating data, making API calls, or manipulating the DOM.
Vue Event Listener
Vue Event Listener: An event listener is a directive that allows a component to listen for a specific event on an element.
Event listeners are declared using the v-on directive, which can be shortened to the @ symbol.
The event listener is added to the element that triggers the event, and it invokes a method or expression when the event occurs.
Here’s an example of a Vue event listener:
In the example above, the @input event listener is attached to an input element. It calls the handleInput method whenever the user types into the input field.
The method receives the event object as an argument, which contains information about the event, such as the target element and the value of the input field.
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Vue Event Bus
Vue Event Bus: An event bus is a global Vue instance that allows communication between components that are not directly related by parent-child relationships.
The event bus acts as a central hub where components can emit and listen to events, enabling them to communicate and share data.
To create an event bus in Vue.js, you can define a new Vue instance and export it as a module:
Now, any component that wants to emit or listen to events can import the event bus and use it:
In the example above, Component A emits a ‘message’ event with a payload, and Component B listens to that event using the event bus.
This allows Component B to receive and react to the message without a direct parent-child relationship.
Vue Event Propagation
Vue Event Propagation: Event propagation refers to the order in which events are handled when multiple elements are nested within each other and an event occurs.
By default, Vue uses a mechanism called event propagation or event bubbling, where an event that is triggered on a nested element will propagate upwards through its parent elements until it reaches the root of the component tree.
During event propagation, Vue triggers event handlers on each element in the propagation path.
This means that if an element has an event handler attached to a specific event, that handler will be executed even if the event originated from a child element.
Here’s an example of Vue event propagation:
In the example above, when you click the “Click me” button, both the child and parent event handlers will be executed. The output in the console will be:
Vue’s event propagation follows the DOM Event Bubbling mechanism, where events start from the innermost element and propagate upwards through the DOM tree.
However, it’s important to note that you can stop event propagation in Vue by calling the event.stopPropagation() method within an event handler.
Vue Event Object
Vue Event Object: The event object is a special object that is automatically passed as an argument to event handlers.
It contains information about the event itself, such as the target element, event type, and any additional data associated with the event.
When an event handler is called, Vue automatically injects the event object as the first argument, allowing you to access its properties and perform actions based on the event data.
Here’s an example of using the event object in a Vue event handler:
In the example above, the handleClick method receives the event object as the event parameter. It logs the event type and the target element to the console.
You can access various properties of the event object, such as event.target to get the target element or event.type to get the type of event that occurred.
The event object provides valuable information and allows you to manipulate the event and its properties within the event handler.
Vue Event Target id
Vue Event Target id: The event target ID refers to the identification of the element that triggered the event.
It allows you to identify the specific element that was interacted with, especially useful when handling events on multiple elements.
To obtain the ID of the target element, you can access the event.target.id property within the event handler.
The id attribute of the HTML element must be set for this property to be meaningful.
Here’s an example of accessing the target ID in a Vue event handler:
In the example above, when you click either “Button 1” or “Button 2”, the handleClick method is called, and it logs the ID of the target element to the console.
If you click “Button 1”, the output will be:
By accessing the target ID, you can differentiate between multiple elements and perform specific actions based on the element that triggered the event.
Is Vue Event Driven?
Yes, Vue.js is indeed event-driven, meaning that it heavily relies on events to facilitate communication between components and trigger actions based on user interactions.
Events are used to allow components to communicate and share data with each other. This communication occurs through a parent-child relationship or between sibling components.
When an event is triggered, Vue.js propagates it through the component hierarchy, enabling parent components to listen and respond to events emitted by child components.
How Do You Emit Events In Vue 2?
Here’s a step-by-step explanation of how to emit events in Vue 2:
Define a custom event in the child component: Within the child component’s template or script section, define the event using the v-on directive.
For example, you can add the following code to emit an event named “custom-event”:
Emit the event: Inside the child component’s code, use the $emit method to trigger the event. You can pass any relevant data as the second argument to $emit.
In the above example, eventData represents the data you want to pass along with the event.
Listen for the event in the parent component: In the parent component’s template, use the v-on directive to listen for the emitted event.
Bind it to a method that will handle the event. For example:
Handle the event in the parent component: In the parent component’s script section, define the handleEvent method to respond to the emitted event.
This method will be executed whenever the custom event is triggered by the child component. For example:
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Hopefully, you now have a better understanding of how you can use Vue Events.
Understanding how you can use Vue Events will help you to send a signal or message to a component with emits to inform other components about a specific action or change in state.
