Technology Sharing

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Ajax and Fetch are both techniques used in JavaScript to send requests from the client to the server to fetch data, but there are some significant differences between them. Here is a detailed comparison of the two techniques:

1. Technical basis and implementation method

1. Ajax：

   • Base: Ajax stands for Asynchronous JavaScript and XML, which is a technology that can update part of a web page without reloading the entire page.
   • Method to realize：Ajax usually uses XMLHttpRequest object to process requests and responses. The syntax of this method is relatively complex, and more code needs to be written to handle callback functions and states.

2. Fetch：

   • Base: Fetch is an API in modern JavaScript that provides common definitions of Request and Response objects for processing network requests.
   • Method to realize：Fetch uses Promise objects to handle asynchronous operations, which can be chained to make the code easier to understand and maintain. Fetch's API style is more concise and powerful.

2. Asynchronous processing and coding style

1. Ajax：

   • Asynchronous Processing: Ajax uses callback functions to handle asynchronous operations, which may lead to the problem of callback hell, especially in complex request chains.
   • Coding style: The Ajax coding style is relatively traditional and requires manual handling of many aspects of requests and responses.

2. Fetch：

   • Asynchronous Processing：Fetch uses Promise objects to handle asynchronous operations, which makes processing asynchronous requests more flexible and concise. You can use async/await to write clear asynchronous code and avoid the problem of callback hell.
   • Coding style: Fetch's code style is more modern and concise, easy to understand and maintain.

3. Cross-domain requests and CORS

1. Ajax：

   • Cross-origin requests: Ajax requests can cross different domain names, but CORS (cross-origin resource sharing) issues need to be properly handled. Ajax can make cross-domain requests through technologies such as JSONP and proxy servers.

2. Fetch：

   • Cross-origin requests: Fetch has stricter restrictions on cross-domain requests because it follows the same-origin policy. If you need to make a cross-domain request, you need to set the appropriate CORS header on the server to allow cross-domain requests. Fetch requests can automatically handle CORS issues, but additional configuration may be required in some cases.

4. Other features

1. Ajax：

   • flexibility: Ajax can customize request headers, request bodies, response formats, etc., providing higher flexibility.
   • compatibility: Ajax may have compatibility issues in older versions of browsers, but with the popularity of modern browsers, this problem has been greatly improved.

2. Fetch：

   • Built-in timeout handling: Fetch can automatically interrupt the request after the request times out, avoiding long waiting.
   • Response Processing: Fetch provides a variety of methods to process response data, such as .json(), .text(), .blob(), etc., making it more convenient to process response data.

usage

fetch It is a modern and powerful network request API in JavaScript that provides a simple and logically clear way to asynchronously obtain resources across the network.fetch Return onePromise, which makes it easy to use with JavaScript's async/await syntax. Here are some basic usage examples:

Basic GET request

fetch('https://api.example.com/data')
  .then(response =
                                   

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