A Comparison of JavaScript HTTP Libraries for the Browser

Modern web development relies heavily on AJAX requests. While the native XMLHttpRequest object provides this functionality, many developers prefer using libraries like jQuery for simpler AJAX handling. This article compares two popular alternatives: superagent and axios, demonstrating their capabilities through requests to a sample HTTP service.

Key Differences:

• Both superagent and axios offer asynchronous AJAX capabilities, allowing other code to execute concurrently.
• Axios leverages Promises, aligning with standard JavaScript practices, while superagent uses a different approach. This makes axios more seamlessly integrable with other promise-based libraries.
• Both are well-suited for basic GET, POST, and PUT requests to APIs but lack features like upload progress monitoring found in modern XMLHttpRequest.
• While functionally similar, the author finds superagent's API more intuitive. However, if Promise integration is crucial, axios is the preferred choice. XMLHttpRequest remains a viable option for developers comfortable managing browser compatibility or targeting modern browsers only.

Library Introduction:

XMLHttpRequest supports both synchronous and asynchronous requests. Since JavaScript is single-threaded, synchronous requests block execution, making asynchronous requests the practical choice. Both axios and superagent exclusively perform asynchronous requests. Because the request happens in the background, the response isn't immediately available. A callback function handles the response once it's received.

Axios uses Promises to manage this process, offering better integration with other asynchronous code. Superagent's API doesn't adhere to standard Promise patterns. This makes axios a more robust option when working with multiple libraries or custom Promises. Superagent, however, boasts wider recognition and a small but useful plugin ecosystem (e.g., for URL prefixing).

Both libraries excel at basic API interaction (GET, POST, PUT), but lack advanced features like upload progress tracking available in modern XMLHttpRequest. Their primary benefit lies in their concise, chainable API for request configuration and execution.

Installation:

XMLHttpRequest requires no installation; it's built into modern browsers (IE8 and later). Superagent is an npm module, requiring npm (included with Node.js/io.js) and a client-side packaging tool like browserify. Axios is available as an npm module, an AMD module, and a standalone JavaScript file.

Example API (Bakery Order Management):

This example uses a hypothetical bakery order management API:

• GET /orders?start=YYYY-MM-DD&end=YYYY-MM-DD: Retrieves orders within a date range.
• POST /orders: Creates a new order.

Data is exchanged in JSON format. For example, to order 3 chocolate and 5 lemon cakes for delivery on March 10th (order placed on May 4th):

{
  "chocolate": "3",
  "lemon": "5",
  "delivery": "2015-03-10",
  "placed": "2015-03-04"
}

Creating a New Order:

This requires specifying the HTTP method (POST), URL (/orders), request body (order details), and content type (application/json).

• Superagent:

var request = require('superagent');

request.post('/orders/')
  .send({'chocolate': 2, 'placed': '2015-04-26'})
  .type('application/json')
  .accept('json')
  .end(function(err, res) {
    if (err) {
      console.log('Error!');
    } else {
      console.log(res.body);
    }
  });

• Axios:

axios.post(
  '/orders/',
  {
    chocolate: 2,
    placed: '2015-04-26'
  },
  {
    headers: {
      'Content-type': 'application/json',
      'Accept': 'application/json'
    }
  }
)
  .then(function(response) {
    console.log(response.data);
  })
  .catch(function(response) {
    console.log('Error!');
  });

• XMLHttpRequest:

var xhr = new XMLHttpRequest();
xhr.open('POST', '/orders/', true);
xhr.setRequestHeader('Content-type', 'application/json');
xhr.setRequestHeader('Accept', 'application/json');
xhr.onload = function() {
  if (xhr.status >= 200 && xhr.status < 300) {
    console.log(xhr.response);
  } else {
    console.log('Error!');
  }
};
xhr.send(JSON.stringify({chocolate: 2, placed: '2015-04-26'}));

Retrieving Orders by Date Range:

This involves adding query parameters (start and end).

• Superagent:

request.get('/orders')
  .query({start: '2015-04-22', end: '2015-04-29'})
  .accept('json')
  .end(function(err, res) {
    // Handle error and response
  });

• Axios:

axios.get(
  '/orders',
  {
    headers: {
      'Accept': 'application/json'
    },
    params: {
      start: '2015-04-22',
      end: '2015-04-29'
    }
  }
);

• XMLHttpRequest:

var xhr = new XMLHttpRequest();
xhr.open('GET', '/orders?start=' + encodeURIComponent('2015-04-22') + '&end=' + encodeURIComponent('2015-04-29'), true);
// ...rest of the code

Recommendations and Conclusion:

Axios and superagent offer similar functionality, with axios's Promise-based approach being a key differentiator. Superagent provides a more streamlined API, but axios's adherence to Promises makes it more versatile. XMLHttpRequest remains a valid option for developers comfortable managing browser-specific nuances. The choice depends on project needs and developer preference. A GitHub repository (link not provided in input) likely contains the complete code examples. The remainder of the input text consists of frequently asked questions and answers which are not included in this output for brevity.

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