GET requests in components in Vue

Introduction

GET requests let your component ask a server for data. This helps your app show fresh information from the internet.

When you want to show a list of items from a website, like news or products.

When you need to load user details after they open a page.

When your app needs to update data without refreshing the whole page.

When you want to fetch weather or other live info to display.

When you build dashboards that show data from online sources.

Syntax

Vue

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

const data = ref(null)
const error = ref(null)

onMounted(async () => {
  try {
    const response = await fetch('https://api.example.com/data')
    if (!response.ok) throw new Error('Network error')
    data.value = await response.json()
  } catch (err) {
    error.value = err.message
  }
})
</script>

Use onMounted to run the GET request when the component appears on screen.

Use ref to store the data and any error so the template can react to changes.

Examples

This example fetches a list of users and stores it in users.

Vue

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

const users = ref([])

onMounted(async () => {
  const res = await fetch('https://jsonplaceholder.typicode.com/users')
  users.value = await res.json()
})
</script>

This example fetches a single post and handles errors if the request fails.

Vue

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

const post = ref(null)
const error = ref(null)

onMounted(async () => {
  try {
    const res = await fetch('https://jsonplaceholder.typicode.com/posts/1')
    if (!res.ok) throw new Error('Failed to load post')
    post.value = await res.json()
  } catch (e) {
    error.value = e.message
  }
})
</script>

Sample Program

This Vue component fetches a list of users when it loads. It shows a loading message while waiting, lists users when ready, and shows an error if the request fails.

Vue

<template>
  <section aria-label="User list">
    <h2>Users</h2>
    <div v-if="error" role="alert" style="color: red">Error: {{ error }}</div>
    <ul v-else-if="users.length">
      <li v-for="user in users" :key="user.id">
        <strong>{{ user.name }}</strong> - {{ user.email }}
      </li>
    </ul>
    <p v-else>Loading users...</p>
  </section>
</template>

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

const users = ref([])
const error = ref(null)

onMounted(async () => {
  try {
    const response = await fetch('https://jsonplaceholder.typicode.com/users')
    if (!response.ok) throw new Error('Network response was not ok')
    users.value = await response.json()
  } catch (err) {
    error.value = err.message
  }
})
</script>

Important Notes

Always handle errors to avoid your app breaking if the server is down or the URL is wrong.

Use semantic HTML and ARIA roles for accessibility, like aria-label and role="alert" for error messages.

Show a loading message so users know data is coming.

Summary

GET requests fetch data from servers to show in your component.

Use onMounted and fetch with async/await inside Vue's <script setup>.

Handle loading, success, and error states for a good user experience.

Practice

1. What is the main purpose of making a GET request inside a Vue component?

easy

A. To delete data on the server

B. To send data from the component to the server

C. To fetch data from a server to display in the component

D. To update the component's local state without server interaction

Solution

1. Step 1: Understand GET request purpose

   A GET request is used to retrieve or fetch data from a server.

2. Step 2: Relate to Vue component usage

   In Vue components, GET requests are used to get data to show in the UI.

3. Final Answer:

   To fetch data from a server to display in the component -> Option C

4. Quick Check:

   GET request = fetch data [OK]

Hint: GET requests retrieve data to show in components [OK]

Common Mistakes:

• Confusing GET with POST (sending data)
• Thinking GET updates local state only
• Mixing GET with delete operations

2. Which of the following is the correct way to import and use the lifecycle hook to run code after a Vue component mounts for a GET request?

easy

A. import { mounted } from 'vue'; mounted(() => { /* fetch code */ });

B. import { onLoad } from 'vue'; onLoad(() => { /* fetch code */ });

C. import { useMounted } from 'vue'; useMounted(() => { /* fetch code */ });

D. import { onMounted } from 'vue'; onMounted(() => { /* fetch code */ });

Solution

1. Step 1: Identify correct lifecycle hook name

   The correct Vue 3 lifecycle hook to run code after component mounts is onMounted.

2. Step 2: Confirm import and usage syntax

   You import it from 'vue' and call it with a function: onMounted(() => { ... }).

3. Final Answer:

   import { onMounted } from 'vue'; onMounted(() => { /* fetch code */ }); -> Option D

4. Quick Check:

   Use onMounted for post-mount code [OK]

Hint: Use onMounted from 'vue' to run code after mount [OK]

Common Mistakes:

• Using wrong hook names like mounted or onLoad
• Forgetting to import onMounted
• Calling lifecycle hooks incorrectly

3. Given this Vue <script setup> snippet, what will be logged to the console after the component mounts?

import { onMounted } from 'vue';

onMounted(async () => {
  const response = await fetch('https://api.example.com/data');
  const data = await response.json();
  console.log(data.message);
});

Assuming the server responds with { "message": "Hello Vue" }.

medium

A. undefined

B. "Hello Vue"

C. SyntaxError

D. An empty object {}

Solution

1. Step 1: Understand fetch and JSON parsing

   The fetch call gets the response, and response.json() parses it into an object.

2. Step 2: Access the message property

   The parsed object has a message key with value "Hello Vue", so console.log(data.message) prints "Hello Vue".

3. Final Answer:

   "Hello Vue" -> Option B

4. Quick Check:

   Fetch JSON message logs "Hello Vue" [OK]

Hint: Fetch + json() returns object; access keys to log values [OK]

Common Mistakes:

• Forgetting to await response.json()
• Logging response instead of parsed data
• Expecting syntax errors from correct async code

4. What is wrong with this Vue <script setup> code that tries to fetch data on mount?

import { onMounted } from 'vue';

onMounted(() => {
  const response = fetch('https://api.example.com/data');
  const data = response.json();
  console.log(data);
});

medium

A. Missing async/await causing response and data to be Promises

B. Using onMounted instead of created hook

C. fetch URL is invalid syntax

D. console.log should be inside a separate function

Solution

1. Step 1: Identify async usage problem

   fetch returns a Promise, so response is a Promise, not the actual response.

2. Step 2: Explain consequence of missing await

   Calling response.json() on a Promise causes data to be a Promise too, so logging it shows a Promise object, not data.

3. Final Answer:

   Missing async/await causing response and data to be Promises -> Option A

4. Quick Check:

   Always await fetch and json() [OK]

Hint: Always use async/await with fetch to get real data [OK]

Common Mistakes:

• Not marking onMounted callback async
• Not awaiting fetch and json() calls
• Expecting immediate data without Promises

5. You want to fetch user data from an API and show a loading message while waiting. Which Vue <script setup> code correctly handles loading, success, and error states for a GET request?

hard

A. import { ref, onMounted } from 'vue';
const user = ref(null);
const loading = ref(true);
const error = ref(null);
onMounted(async () => {
try {
const res = await fetch('https://api.example.com/user');
if (!res.ok) throw new Error('Fetch failed');
user.value = await res.json();
} catch (e) {
error.value = e.message;
} finally {
loading.value = false;
}
});

B. import { ref, onMounted } from 'vue';
const user = ref(null);
const loading = false;
const error = null;
onMounted(() => {
fetch('https://api.example.com/user')
.then(res => res.json())
.then(data => user.value = data)
.catch(e => error = e.message);
loading = false;
});

C. import { reactive, onMounted } from 'vue';
const state = reactive({ user: null, loading: false, error: null });
onMounted(async () => {
const res = await fetch('https://api.example.com/user');
state.user = await res.json();
state.loading = false;
});

D. import { ref, onMounted } from 'vue';
const user = ref(null);
const loading = ref(false);
const error = ref(null);
onMounted(async () => {
loading.value = true;
const res = await fetch('https://api.example.com/user');
user.value = await res.json();
loading.value = false;
});

Solution

1. Step 1: Check reactive state setup

   import { ref, onMounted } from 'vue'; const user = ref(null); const loading = ref(true); const error = ref(null); onMounted(async () => { try { const res = await fetch('https://api.example.com/user'); if (!res.ok) throw new Error('Fetch failed'); user.value = await res.json(); } catch (e) { error.value = e.message; } finally { loading.value = false; } }); uses ref for user, loading, and error, properly reactive for Vue.

2. Step 2: Verify async fetch with error handling

   import { ref, onMounted } from 'vue'; const user = ref(null); const loading = ref(true); const error = ref(null); onMounted(async () => { try { const res = await fetch('https://api.example.com/user'); if (!res.ok) throw new Error('Fetch failed'); user.value = await res.json(); } catch (e) { error.value = e.message; } finally { loading.value = false; } }); uses async/await with try/catch/finally to handle success, errors, and loading state correctly.

3. Final Answer:

   Option A correctly manages loading, success, and error states with reactive refs and proper async handling. -> Option A

4. Quick Check:

   Use refs + async try/catch/finally for GET with states [OK]

Hint: Use refs and try/catch/finally for loading and error states [OK]

Common Mistakes:

• Not using reactive refs for loading and error
• Setting loading false too early or outside async flow
• Ignoring error handling in fetch