Why API integration connects to backends in React Native - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to fetch data from the backend API.

React Native

fetch('https://api.example.com/data')
  .then(response => response.[1]())
  .then(data => console.log(data));

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

Ajson

Btext

Cxml

Dblob

Attempts:

3 left

💡 Hint

Common Mistakes

Using text() instead of json() causes data to be a string, not an object.

The json() method parses the response as JSON, which is the common data format from APIs.

2fill in blank

medium

Complete the code to send a POST request to the backend API.

React Native

fetch('https://api.example.com/login', {
  method: '[1]',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({ username: 'user', password: 'pass' })
});

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

AGET

BPUT

CPOST

DDELETE

Attempts:

3 left

💡 Hint

Common Mistakes

Using GET method with a body does not send data properly.

POST method is used to send data to the backend, such as login credentials.

3fill in blank

hard

Fix the error in the code to correctly handle API response errors.

React Native

fetch('https://api.example.com/data')
  .then(response => {
    if (!response.[1]) {
      throw new Error('Network response was not ok');
    }
    return response.json();
  })
  .catch(error => console.error('Fetch error:', error));

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

Aok

Bstatus

Cjson

Dbody

Attempts:

3 left

💡 Hint

Common Mistakes

Checking status directly without comparing to a range.

The ok property is a boolean indicating if the response status is in the 200-299 range.

4fill in blank

hard

Fill both blanks to create a React Native component that fetches data on button press.

React Native

import React, { useState } from 'react';
import { Button, Text, View } from 'react-native';

export default function App() {
  const [data, setData] = useState(null);

  const fetchData = async () => {
    const response = await fetch('https://api.example.com/data');
    const json = await response.[1]();
    setData(json.[2]);
  };

  return (
    <View>
      <Button title="Load Data" onPress={fetchData} />
      <Text>{data}</Text>
    </View>
  );
}

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

Ajson

Btext

Cmessage

Dresult

Attempts:

3 left

💡 Hint

Common Mistakes

Using text() instead of json(), or accessing a wrong property.

Use json() to parse the response, then access the result property from the JSON data.

5fill in blank

hard

Fill all three blanks to complete the React Native fetch with error handling and loading state.

React Native

import React, { useState } from 'react';
import { Button, Text, View, ActivityIndicator } from 'react-native';

export default function App() {
  const [data, setData] = useState(null);
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState(null);

  const fetchData = async () => {
    setLoading(true);
    setError(null);
    try {
      const response = await fetch('https://api.example.com/data');
      if (!response.[1]) throw new Error('Error fetching');
      const json = await response.[2]();
      setData(json.[3]);
    } catch (e) {
      setError(e.message);
    } finally {
      setLoading(false);
    }
  };

  return (
    <View>
      <Button title="Load" onPress={fetchData} />
      {loading && <ActivityIndicator />}
      {error && <Text>Error: {error}</Text>}
      {data && <Text>{data}</Text>}
    </View>
  );
}

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

Aok

Bjson

Cresult

Dstatus

Attempts:

3 left

💡 Hint

Common Mistakes

Not checking response.ok, or using wrong property names.

Check ok to confirm response success, parse JSON with json(), then access result property.

Practice

1. Why does a React Native app use API integration to connect to a backend server?

easy

A. To get or send data between the app and the server

B. To change the app's color scheme automatically

C. To increase the app's font size on the screen

D. To store data only on the user's device

Solution

1. Step 1: Understand the role of backend servers

   Backend servers store and manage data that apps need to access or update.

2. Step 2: Recognize API integration purpose

   API integration allows the app to communicate with the backend to get or send this data.

3. Final Answer:

   To get or send data between the app and the server -> Option A

4. Quick Check:

   API integration connects app and backend data [OK]

Hint: API integration moves data between app and server [OK]

Common Mistakes:

• Thinking API changes app design automatically
• Confusing local storage with backend data
• Believing API only changes UI elements

2. Which of the following is the correct way to fetch data from an API in React Native using async/await?

easy

A. const data = fetch('https://api.example.com/data').json();

B. const response = await fetch('https://api.example.com/data'); const data = await response.json();

C. fetch('https://api.example.com/data').then(response => response.text());

D. await fetch('https://api.example.com/data').json();

Solution

1. Step 1: Use fetch with await to get response

   fetch returns a promise; await waits for it to resolve to a response object.

2. Step 2: Use await on response.json() to parse JSON data

   response.json() returns a promise that resolves to the parsed data.

3. Final Answer:

   const response = await fetch('https://api.example.com/data'); const data = await response.json(); -> Option B

4. Quick Check:

   Use await twice: fetch and json() [OK]

Hint: Await fetch, then await response.json() [OK]

Common Mistakes:

• Calling json() directly on fetch without await
• Using response.text() instead of response.json()
• Missing await keyword causing unresolved promises

3. What will be logged to the console after this React Native code runs?

async function getData() {
  const response = await fetch('https://api.example.com/user');
  const user = await response.json();
  console.log(user.name);
}
getData();

medium

A. The entire user object printed as a string

B. undefined

C. An error because fetch is not awaited

D. The user's name from the API response

Solution

1. Step 1: Await fetch and parse JSON

   The code waits for the fetch call and parses the JSON response into the user object.

2. Step 2: Log the user's name property

   console.log prints the value of user.name from the parsed object.

3. Final Answer:

   The user's name from the API response -> Option D

4. Quick Check:

   Await fetch and json() gives user.name [OK]

Hint: Await fetch and json() before accessing data [OK]

Common Mistakes:

• Forgetting await causing unresolved promises
• Logging user instead of user.name
• Assuming fetch returns data directly without parsing

4. Identify the error in this React Native API call code:

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

medium

A. Using await on response.json() is incorrect

B. fetch URL is invalid syntax

C. Missing await before fetch causing response to be a promise

D. console.log should be inside a .then() block

Solution

1. Step 1: Check fetch call usage

   fetch returns a promise, so it must be awaited to get the response object.

2. Step 2: Identify consequence of missing await

   Without await, response is a promise, so calling response.json() causes an error.

3. Final Answer:

   Missing await before fetch causing response to be a promise -> Option C

4. Quick Check:

   Always await fetch before response.json() [OK]

Hint: Await fetch before calling response.json() [OK]

Common Mistakes:

• Assuming fetch returns data immediately
• Calling json() on a promise instead of response
• Misunderstanding async/await order

5. You want your React Native app to show updated weather data every time the user opens the app. Which approach best uses API integration to achieve this?

hard

A. Call the weather API inside a useEffect hook that runs on component mount

B. Store weather data once in a variable and never update it

C. Fetch weather data only when the user presses a button

D. Hardcode weather data in the app code

Solution

1. Step 1: Understand when to fetch updated data

   To get fresh data each time the app opens, fetch on component mount is ideal.

2. Step 2: Use React Native lifecycle with useEffect

   useEffect with empty dependency array runs once on mount, perfect for initial API call.

3. Final Answer:

   Call the weather API inside a useEffect hook that runs on component mount -> Option A

4. Quick Check:

   useEffect on mount fetches fresh data [OK]

Hint: Fetch data on mount with useEffect [OK]

Common Mistakes:

• Not updating data after first load
• Fetching only on user action missing auto updates
• Hardcoding data prevents real-time updates