Passing arguments to handlers in Vue - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to pass the event object to the handler.

Vue

<template>
  <button @click="handleClick([1])">Click me</button>
</template>

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

Drag options to blanks, or click blank then click option'

A$event

Bevent

Cthis

Dclick

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'event' directly without $ sign.

Passing a string like 'click' instead of the event object.

In Vue, to pass the native event object to a handler, use $event.

2fill in blank

medium

Complete the code to pass a custom argument '42' to the handler.

Vue

<template>
  <button @click="handleClick([1])">Click me</button>
</template>

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

Drag options to blanks, or click blank then click option'

A'42'

Bid

C42

D$event

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the number as a string with quotes.

Using a variable name that is not defined.

To pass a number argument to a handler, just write the number without quotes.

3fill in blank

hard

Fix the error in passing both event and a custom argument to the handler.

Vue

<template>
  <button @click="handleClick([1], 5)">Click me</button>
</template>

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

Drag options to blanks, or click blank then click option'

A5

B$event

Cnumber

Devent

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'event' without $ sign.

Passing the number as the first argument.

Use $event to pass the native event object as the first argument.

4fill in blank

hard

Fill both blanks to pass event and a custom message to the handler.

Vue

<template>
  <button @click="handleClick([1], [2])">Click me</button>
</template>

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

Drag options to blanks, or click blank then click option'

A$event

B'Hello'

CHello

Devent

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the string without quotes.

Using 'event' instead of '$event'.

Pass $event for the event and a string with quotes for the message.

5fill in blank

hard

Fill all three blanks to pass event, id, and a flag to the handler.

Vue

<template>
  <button @click="handleClick([1], [2], [3])">Click me</button>
</template>

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

Drag options to blanks, or click blank then click option'

A$event

B10

Ctrue

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Passing booleans as strings.

Using 'event' instead of '$event'.

Pass $event for the event, a number for id, and a boolean for flag.

Practice

1. In Vue, how do you pass an argument 42 to a click event handler named handleClick in the template?

easy

A. @click="handleClick:42"

B. @click="handleClick"

C. @click="handleClick(42)"

D. @click="handleClick=>42"

Solution

1. Step 1: Understand Vue event binding syntax

   Vue uses @click to bind click events and parentheses to pass arguments.

2. Step 2: Passing argument 42 to handler

   Using @click="handleClick(42)" calls handleClick with argument 42 on click.

3. Final Answer:

   @click="handleClick(42)" -> Option C

4. Quick Check:

   Use parentheses to pass arguments [OK]

Hint: Use parentheses after handler name to pass arguments [OK]

Common Mistakes:

• Omitting parentheses when passing arguments
• Using colon or arrow instead of parentheses
• Passing argument without quotes for strings

2. Which of the following is the correct syntax to pass a string argument 'hello' to a method sayHello in Vue template?

easy

A. @click="sayHello(hello)"

B. @click="sayHello('hello')"

C. @click="sayHello:"hello""

D. @click="sayHello{hello}"

Solution

1. Step 1: Recognize string argument syntax

   Strings must be wrapped in quotes inside parentheses when passed as arguments.

2. Step 2: Check each option

   Only @click="sayHello('hello')" correctly passes the string 'hello'. Others are invalid syntax.

3. Final Answer:

   @click="sayHello('hello')" -> Option B

4. Quick Check:

   Strings need quotes inside parentheses [OK]

Hint: Wrap string arguments in quotes inside parentheses [OK]

Common Mistakes:

• Passing string without quotes
• Using colon or braces instead of parentheses
• Confusing variable name with string literal

3. Given this Vue template snippet:

<button @click="increment(5)">Add 5</button>
<script setup>
import { ref } from 'vue'
const count = ref(0)
function increment(amount) {
  count.value += amount
}
</script>

What will be the value of count.value after clicking the button twice?

medium

A. 5

B. Error: amount undefined

C. 0

D. 10

Solution

1. Step 1: Understand initial state and handler

   Initially, count.value is 0. The increment function adds the passed amount to count.value.

2. Step 2: Calculate after two clicks

   Each click adds 5, so after two clicks: 0 + 5 + 5 = 10.

3. Final Answer:

   10 -> Option D

4. Quick Check:

   2 clicks x 5 each = 10 [OK]

Hint: Multiply clicks by argument to find new value [OK]

Common Mistakes:

• Assuming count resets after each click
• Forgetting to add amount to count
• Confusing ref value access syntax

4. What is wrong with this Vue template code?

<button @click="submitForm(formData)">Submit</button>
<script setup>
const formData = { name: 'Alice' }
function submitForm() {
  console.log(formData)
}
</script>

medium

A. The handler does not accept the argument passed

B. The formData object is not reactive

C. The event object is missing

D. The button tag is invalid

Solution

1. Step 1: Check handler parameters

   The template passes formData as an argument, but submitForm has no parameters defined.

2. Step 2: Understand mismatch effect

   This causes the argument to be ignored and may confuse the handler logic expecting parameters.

3. Final Answer:

   The handler does not accept the argument passed -> Option A

4. Quick Check:

   Handler must declare parameters to receive arguments [OK]

Hint: Match handler parameters with passed arguments [OK]

Common Mistakes:

• Not defining parameters in handler function
• Assuming reactive needed for argument passing
• Confusing event object with custom arguments

5. You want to pass both a custom argument id and the native event object to a Vue method handleClick. Which is the correct way to do this in the template?

hard

A. @click="handleClick(id, $event)"

B. @click="handleClick($event, id)"

C. @click="handleClick(id)"

D. @click="handleClick()"

Solution

1. Step 1: Understand argument order

   To pass both a custom argument and the event, list them in order inside parentheses.

2. Step 2: Use $event for native event

   $event is Vue's special variable for the native event object.

3. Step 3: Confirm correct syntax

   @click="handleClick(id, $event)" correctly passes id first, then the event.

4. Final Answer:

   @click="handleClick(id, $event)" -> Option A

5. Quick Check:

   Pass custom args before $event [OK]

Hint: Pass $event last to get native event object [OK]

Common Mistakes:

• Passing $event before custom arguments
• Forgetting to include $event for event object
• Calling handler without parentheses