Accessing the native event object in Vue - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output when clicking the button?

Consider this Vue 3 component using the Composition API. What will be logged to the console when the button is clicked?

Vue

<template>
  <button @click="handleClick">Click me</button>
</template>

<script setup>
import { ref } from 'vue'

function handleClick(event) {
  console.log(event.target.tagName)
}
</script>

A null

B "button"

C "BUTTON"

D undefined

💡 Hint

Remember that event.target refers to the element that triggered the event, and tagName returns the tag in uppercase.

The native event object has a target property pointing to the clicked element. The tagName property returns the tag name in uppercase, so it logs "BUTTON".

📝 Syntax

intermediate

Which option correctly accesses the native event object in Vue 3?

In Vue 3, you want to access the native event object inside a method triggered by a click. Which code snippet correctly receives the event?

A

<button @click="handleClick()">Click</button>

<script setup>
function handleClick(event) {
  console.log(event.type)
}
</script>

B

<button @click="handleClick($event)">Click</button>

<script setup>
function handleClick(event) {
  console.log(event.type)
}
</script>

C

<button @click="handleClick">Click</button>

<script setup>
function handleClick() {
  console.log(event.type)
}
</script>

D

<button @click="handleClick">Click</button>

<script setup>
function handleClick(event) {
  console.log(event.nativeEvent.type)
}
</script>

💡 Hint

Vue automatically passes the native event object as the first argument if you use $event in the template.

Option B explicitly passes $event to the handler, so the function receives the native event object. Other options either omit the event or incorrectly access it.

🔧 Debug

advanced

Why does this Vue 3 code cause an error when accessing the event?

Examine this Vue 3 component code. Why does it cause a runtime error when clicking the button?

Vue

<template>
  <button @click="handleClick">Click me</button>
</template>

<script setup>
function handleClick() {
  console.log(event.type)
}
</script>

A "event" is not defined inside the function scope, causing a ReferenceError.

B The event object is null because the button has no event attached.

C The event object is undefined because Vue 3 does not support native events.

D The event object is accessible only in the template, not in script setup.

💡 Hint

Check how the event object is passed to event handlers in Vue 3.

The function handleClick does not receive any parameters, so event is undefined inside it. This causes a ReferenceError when trying to access event.type.

❓ state_output

advanced

What is the value of count after clicking the button twice?

In this Vue 3 component, what will be the value of count after clicking the button two times?

Vue

<template>
  <button @click="increment">Click me</button>
  <p>{{ count }}</p>
</template>

<script setup>
import { ref } from 'vue'
const count = ref(0)

function increment(event) {
  if (event.isTrusted) {
    count.value += 1
  }
}
</script>

A 2

B NaN

C 0

D 1

💡 Hint

The isTrusted property is true for user-generated events.

Each click triggers increment with a trusted event, so count.value increases by 1 each time. After two clicks, count is 2.

🧠 Conceptual

expert

Which statement about accessing native events in Vue 3 is correct?

Choose the correct statement about how Vue 3 handles native event objects in event handlers.

A Vue 3 automatically passes the native event object as the first argument to event handlers without needing <code>$event</code>.

B Vue 3 replaces the native event object with a custom event object that lacks standard properties like <code>target</code>.

C The native event object is accessible via <code>this.$event</code> inside the handler function in Vue 3's Composition API.

D You must explicitly pass <code>$event</code> in the template to receive the native event object in the handler function.

💡 Hint

Think about how event arguments are passed in Vue 3 templates.

In Vue 3, to access the native event object inside a handler, you must pass $event explicitly in the template. Vue does not automatically pass it.