Loading states pattern in Vue - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a reactive loading state using Vue's Composition API.

Vue

import { [1] } from 'vue';

const isLoading = [1](false);

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

Awatch

Breactive

Ccomputed

Dref

Attempts:

3 left

💡 Hint

Common Mistakes

Using reactive instead of ref for a single boolean value.

Forgetting to import the function from 'vue'.

We use ref to create a simple reactive variable for loading state.

2fill in blank

medium

Complete the code to toggle the loading state to true when a function starts.

Vue

function fetchData() {
  isLoading.[1] = true;
  // simulate data fetch
}

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

Astate

Bloading

Cvalue

Dset

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to assign directly to the ref variable without .value.

Using a non-existent property like 'loading' or 'state'.

When using ref, the actual value is accessed and set via the .value property.

3fill in blank

hard

Fix the error in the template to show 'Loading...' only when loading is true.

Vue

<template>
  <div v-if="[1]">Loading...</div>
</template>

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

Aloading

BisLoading

Cisloading

Dload

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name with wrong casing.

Using a variable name that was never declared.

The reactive variable is named isLoading and must match exactly in the template.

4fill in blank

hard

Fill both blanks to create a reactive object with loading and data properties.

Vue

import { [1] } from 'vue';

const state = [2]({ loading: false, data: null });

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

Areactive

Bref

Ccomputed

Dwatch

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing ref and reactive incorrectly.

Using computed or watch instead of reactive.

Use reactive to create a reactive object with multiple properties.

5fill in blank

hard

Fill all three blanks to create a loading state, fetch data asynchronously, and update the state.

Vue

import { [1] } from 'vue';

const isLoading = [2](false);

async function loadData() {
  isLoading.[3] = true;
  await fetch('https://api.example.com/data');
  isLoading.value = false;
}

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

Aref

Breactive

Cvalue

Dloading

Attempts:

3 left

💡 Hint

Common Mistakes

Using reactive instead of ref for a boolean.

Assigning to isLoading directly without .value.

We import and use ref to create isLoading. The value is accessed and set with .value.

Practice

1. What is the main purpose of using a loading state in a Vue component?

easy

A. To disable Vue reactivity

B. To show users that data is being fetched or processed

C. To permanently hide content from users

D. To increase the component's size

Solution

1. Step 1: Understand user experience during data fetching

   Loading states inform users that the app is working on a task, preventing confusion.

2. Step 2: Identify the purpose of loading states in Vue

   They show progress or waiting messages while data loads or actions complete.

3. Final Answer:

   To show users that data is being fetched or processed -> Option B

4. Quick Check:

   Loading states = user feedback [OK]

Hint: Loading states show progress to users during waits [OK]

Common Mistakes:

• Thinking loading states hide content permanently
• Confusing loading states with disabling reactivity
• Assuming loading states change component size

2. Which Vue syntax correctly shows a loading message only when isLoading is true?

easy

A. <div v-show="isLoading">Loading...</div>

B. <div v-if="!isLoading">Loading...</div>

C. <div v-if="isLoading">Loading...</div>

D. <div v-bind:isLoading>Loading...</div>

Solution

1. Step 1: Understand v-if usage

   v-if conditionally renders the element only if the expression is true.

2. Step 2: Match condition to show loading

   We want to show the message when isLoading is true, so v-if="isLoading" is correct.

3. Final Answer:

   <div v-if="isLoading">Loading...</div> -> Option C

4. Quick Check:

   Show loading if isLoading true = v-if="isLoading" [OK]

Hint: Use v-if with the loading variable directly [OK]

Common Mistakes:

• Using v-if with negation (!isLoading) to show loading
• Using v-show which toggles visibility but keeps element
• Using invalid v-bind syntax for conditional rendering

3. Given this Vue setup:

const isLoading = ref(true);
setTimeout(() => { isLoading.value = false; }, 2000);

What will the component show initially if template has <div v-if="isLoading">Loading...</div><div v-else>Content Loaded</div>?

medium

A. Loading... for 2 seconds, then Content Loaded

B. Content Loaded immediately

C. Nothing is shown

D. Loading... forever

Solution

1. Step 1: Analyze initial value of isLoading

   It starts as true, so v-if="isLoading" shows "Loading..." initially.

2. Step 2: Understand the timeout effect

   After 2 seconds, isLoading.value becomes false, switching to v-else content "Content Loaded".

3. Final Answer:

   Loading... for 2 seconds, then Content Loaded -> Option A

4. Quick Check:

   Initial true shows loading, then false shows content [OK]

Hint: Check initial state and delayed change for output [OK]

Common Mistakes:

• Assuming content shows immediately ignoring initial true
• Thinking loading never stops without reactivity knowledge
• Confusing v-if and v-else rendering timing

4. Identify the error in this Vue code snippet for loading state:

const isLoading = ref(false);

function fetchData() {
  isLoading = true;
  fetch('/api/data')
    .then(() => { isLoading = false; });
}

medium

A. No error, code works fine

B. Missing async keyword on fetchData function

C. fetch API call is incorrect syntax

D. Directly assigning to ref variable instead of its .value

Solution

1. Step 1: Understand how to update Vue refs

   Refs are objects; their value must be changed via .value, not by direct assignment.

2. Step 2: Identify incorrect assignments

   Code assigns isLoading = true instead of isLoading.value = true, causing errors.

3. Final Answer:

   Directly assigning to ref variable instead of its .value -> Option D

4. Quick Check:

   Update ref with .value, not direct assignment [OK]

Hint: Change ref values with .value property [OK]

Common Mistakes:

• Assigning ref variable directly instead of .value
• Forgetting to handle promise with then or async/await
• Assuming fetch syntax is wrong when it is correct

5. You want to disable a submit button during loading in Vue. Which code snippet correctly disables the button and shows loading text using isLoading reactive variable?

hard

A. <button :disabled="isLoading">{{ isLoading ? 'Loading...' : 'Submit' }}</button>

B. <button v-if="isLoading" disabled>Submit</button><button v-else>Loading...</button>

C. <button :disabled="!isLoading">Submit</button>

D. <button :loading="isLoading">Submit</button>

Solution

1. Step 1: Disable button based on loading state

   Use :disabled="isLoading" to disable the button when loading.

2. Step 2: Show dynamic button text

   Use interpolation with a ternary to show "Loading..." or "Submit" based on isLoading.

3. Final Answer:

   <button :disabled="isLoading">{{ isLoading ? 'Loading...' : 'Submit' }}</button> -> Option A

4. Quick Check:

   Disable button and show loading text with :disabled and ternary [OK]

Hint: Bind :disabled and use ternary text inside button [OK]

Common Mistakes:

• Using v-if to swap buttons instead of disabling
• Negating isLoading for disabling logic
• Using non-existent :loading attribute on button