Fetch API and Error Handling in JavaScript

JavaScript Event Handling: Exercise-18 with Solution

Fetch API with Error Handling

Write a JavaScript program that fetches data from an API, handles network errors, and displays the results on a webpage

Solution 1: Using fetch data from an API

JavaScript Code:

// Function to fetch data from an API and display it
async function fetchData() {
  const apiUrl = 'https://jsonplaceholder.typicode.com/posts'; // API endpoint
  const resultContainer = document.getElementById('result'); // Div to display results

  try {
    const response = await fetch(apiUrl); // Fetch data from the API

    if (!response.ok) {
      throw new Error(`HTTP error! status: ${response.status}`); // Handle non-200 responses
    }

    const data = await response.json(); // Parse the response as JSON
    displayResults(data); // Call function to display the results
  } catch (error) {
    console.error('Fetch failed:', error); // Log errors to the console
    resultContainer.textContent = 'Error fetching data. Please try again later.'; // Show error message
  }
}

// Function to display fetched data
function displayResults(data) {
  const resultContainer = document.getElementById('result'); // Div to display results
  resultContainer.innerHTML = ''; // Clear previous content

  data.slice(0, 5).forEach((item) => {
    const p = document.createElement('p'); // Create a paragraph for each result
    p.textContent = `Post ${item.id}: ${item.title}`; // Add the title of each post
    resultContainer.appendChild(p); // Append the paragraph to the container
  });
}

// Add a button to trigger data fetch
const fetchButton = document.createElement('button');
fetchButton.textContent = 'Fetch Data'; // Button text
fetchButton.onclick = fetchData; // Set click event to fetch data
document.body.appendChild(fetchButton); // Add button to the DOM

// Add a container to display results
const resultContainer = document.createElement('div');
resultContainer.id = 'result'; // Set ID for styling or reference
document.body.appendChild(resultContainer); // Add container to the DOM

Output:

Fetch Data
Post 1: sunt aut facere repellat provident occaecati excepturi optio reprehenderit

Post 2: qui est esse

Post 3: ea molestias quasi exercitationem repellat qui ipsa sit aut

Post 4: eum et est occaecati

Post 5: nesciunt quas odio

Explanation:

1. Fetching Data:

• Uses the fetch API inside a try-catch block for better error handling.

2. Error Handling:

• Checks if the response is not OK and throws an error with the HTTP status.
• Catches both network errors and non-200 responses.

3. Display Results:

• Dynamically displays the first 5 posts in a styled div.

4. User Interaction:

• Adds a button to trigger the fetch operation, ensuring flexibility.

Solution 2: Using Fetch with Promises

JavaScript Code:

// Function to fetch data from an API and display it
function fetchData() {
  const apiUrl = 'https://jsonplaceholder.typicode.com/posts'; // API endpoint
  const resultContainer = document.getElementById('result'); // Div to display results

  fetch(apiUrl)
    .then((response) => {
      if (!response.ok) {
        throw new Error(`HTTP error! status: ${response.status}`); // Handle non-200 responses
      }
      return response.json(); // Parse the response as JSON
    })
    .then((data) => {
      displayResults(data); // Call function to display the results
    })
    .catch((error) => {
      console.error('Fetch failed:', error); // Log errors to the console
      resultContainer.textContent = 'Error fetching data. Please try again later.'; // Show error message
    });
}

// Function to display fetched data
function displayResults(data) {
  const resultContainer = document.getElementById('result'); // Div to display results
  resultContainer.innerHTML = ''; // Clear previous content

  data.slice(0, 5).forEach((item) => {
    const p = document.createElement('p'); // Create a paragraph for each result
    p.textContent = `Post ${item.id}: ${item.title}`; // Add the title of each post
    resultContainer.appendChild(p); // Append the paragraph to the container
  });
}

// Add a button to trigger data fetch
const fetchButton = document.createElement('button');
fetchButton.textContent = 'Fetch Data'; // Button text
fetchButton.onclick = fetchData; // Set click event to fetch data
document.body.appendChild(fetchButton); // Add button to the DOM

// Add a container to display results
const resultContainer = document.createElement('div');
resultContainer.id = 'result'; // Set ID for styling or reference
document.body.appendChild(resultContainer); // Add container to the DOM

Output:

Fetch Data
Post 1: sunt aut facere repellat provident occaecati excepturi optio reprehenderit

Post 2: qui est esse

Post 3: ea molestias quasi exercitationem repellat qui ipsa sit aut

Post 4: eum et est occaecati

Post 5: nesciunt quas odio

Explanation:

1. Fetching Data:

• Uses the fetch API with Promises (then and catch) for handling asynchronous behavior.

2. Error Handling:

• Throws an error for non-200 HTTP responses and catches it in the catch block.

3. Display Results:

• Dynamically displays the first 5 posts in a styled div.

4. User Interaction:

• Adds a button to trigger the fetch operation, ensuring the user initiates the request.

Live Demo:

See the Pen javascript-event-handling-exercise-18 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that fetches data from a public API, checks for HTTP errors, and displays a custom error message if needed.
• Write a JavaScript function that uses the Fetch API to retrieve data, implements a timeout for the request, and handles errors gracefully.
• Write a JavaScript program that fetches JSON data from an API and retries the request upon encountering network errors.
• Write a JavaScript function that parses API responses and uses try-catch to handle JSON parsing errors.

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