Detailed explanation and code examples of the use of AJAX, Axios and Fetch in comprehensive analysis of front-end requests

Preface

In front-end development, interacting with back-end data is a very common requirement. From traditional AJAX to modern fetch APIs to popular third-party library Axios, all solutions have their pros and cons. This article will analyze the principles, usage methods and code examples of these three request methods one by one to help you choose a solution that suits the needs of the project.

1. AJAX - Traditional asynchronous requests

AJAX (Asynchronous JavaScript and XML) is the earliest technology to implement asynchronous requests from browsers, mainly based on XMLHttpRequest object. Although we are more inclined to use Promise-based solutions today, understanding the principles of AJAX can still help to gain a deep understanding of the underlying implementation of HTTP requests.

1.1 Basic usage examples

Here is an example of using XMLHttpRequest to initiate a GET request:

// Create XMLHttpRequest objectvar xhr = new XMLHttpRequest();

// Initialization request: GET method, asynchronous request("GET", "/data", true);

// Listen to request status changes = function() {
  if ( === 4) { // Request complete    if ( === 200) { // Return successfully      ("AJAX Success:", );
    } else { // Error handling      ("AJAX Error:", );
    }
  }
};

// Send a request();

1.2 AJAX Features

Good compatibility: Almost all browsers support XMLHttpRequest.
Callback function: The response needs to be processed through the onreadystatechange callback, and the code structure is relatively lengthy and not intuitive enough.
Data format: Originally mainly used to transfer XML, but now it is often used in data formats such as JSON.

2. Fetch API - Modern Request Solution

The Fetch API is a native asynchronous request interface provided by the browser. It is implemented based on Promise and is more in line with modern JavaScript programming habits. It makes the code more concise, easy to read, and supports richer request configurations.

2.1 Basic usage examples

The sample code for initiating a GET request using fetch is as follows:

fetch("/data")
  .then(response =&gt; {
    // Check the response status    if (!) {
      throw new Error("Network response was not ok, status: " + );
    }
    // parse JSON data    return ();
  })
  .then(data =&gt; {
    ("Fetch Success:", data);
  })
  .catch(error =&gt; {
    ("Fetch Error:", error);
  });

2.2 Fetch Features

Simple and easy to use: Based on Promise, there is no need to write complex callback functions.
Response processing: Supports chain calls, and can easily process response data (such as JSON, Blob, Text, etc.).
Flexible configuration: The request method, header information, request body, etc. can be set through configuration options.

3. Axios - Third-party HTTP Request Library

Axios is a Promise-based HTTP client that is compatible with browsers and environments. It provides rich functions such as request interception, response interception, cancel requests, automatic conversion of JSON data, etc., and is widely used in actual projects.

3.1 Install Axios

Install via npm or yarn:

# Install using npmnpm install axios

# Or use yarn to installyarn add axios

3.2 Basic usage examples

The sample code for initiating a GET request using Axios is as follows:

import axios from "axios";

("/data")
  .then(response => {
    ("Axios Success:", );
  })
  .catch(error => {
    ("Axios Error:", error);
  });

Similarly, you can use Axios to initiate a POST request:

("/data", {
    name: "John Doe",
    age: 30
  })
  .then(response => {
    ("Axios POST Success:", );
  })
  .catch(error => {
    ("Axios POST Error:", error);
  });

3.3 Axios Features

Automatically handle JSON: The request and response data are automatically converted to JSON.
Interceptor: Request and response interceptors can be configured globally to facilitate unified processing of errors, add authentication information, etc.
More richer features: Supports advanced functions such as cancellation requests, timeout settings, and concurrent request processing.

4. Summary

In front-end projects, different request solutions have their own advantages and disadvantages:

AJAX（XMLHttpRequest）: Suitable for understanding the underlying principles, but the code structure is relatively complex and is rarely used directly in new projects.
Fetch API: Concise syntax, Promise-based, suitable for modern browsers, but you need to pay attention to manual handling of error status.
Axios: Feature-rich, supports interceptors and more advanced features, suitable for large projects and complex needs.

Depending on project needs and team habits, choosing the right request method can greatly improve development efficiency and code maintainability. I hope that the detailed explanation and code examples of this article can provide reference and help in the development practice of front-end requests!

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