Exploring the Potential of AJAX Properties: Secrets of Amazing Power Revealed

AJAX attribute analysis: wonderful functions you don’t know

Introduction:
In modern Web development, AJAX (Asynchronous JavaScript and XML) is a very Important concept. It allows us to communicate asynchronously with the web server and update page content via JavaScript without reloading the entire page. In addition to common basic usage, AJAX also has some powerful and magical functions. This article will explore these functions in depth and provide specific code examples.

I. Dynamically loading CSS style sheets
AJAX can be used not only to load XML, JSON or HTML data, but also to load CSS style sheets. By using AJAX to load the style sheet asynchronously, we can apply styles step by step as the page loads, rather than waiting for the entire style sheet to load before applying it. This is very helpful for improving page performance and user experience.
Code example:

var xhr = new XMLHttpRequest();
xhr.open("GET", "styles.css", true);
xhr.onreadystatechange = function() {
  if (xhr.readyState === 4 && xhr.status === 200) {
    var style = document.createElement("style");
    style.innerHTML = xhr.responseText;
    document.head.appendChild(style);
  }
};
xhr.send();

II. File upload progress prompt
In the traditional file upload process, the upload progress cannot be displayed, and the result can only be known after the upload is completed. However, using AJAX, we can get the progress information of the file upload and display it to the user in real time to provide better feedback and user experience.
Code example:

var xhr = new XMLHttpRequest();
xhr.open("POST", "upload.php", true);
xhr.upload.onprogress = function(e) {
  if (e.lengthComputable) {
    var percent = (e.loaded / e.total) * 100;
    console.log("上传进度：" + percent + "%");
  }
};
xhr.send(formData);

In this example, we can obtain the upload progress information by listening to the xhr.upload.onprogress event, and then process it as needed.

III. Cross-domain requests
AJAX was originally designed for same-domain requests, that is, it can only request resources under the same domain name. However, through some special technical means, we can use AJAX to make cross-domain requests, that is, send AJAX requests from pages in one domain name to pages in other domain names.
Code example:

var xhr = new XMLHttpRequest();
xhr.open("GET", "http://example.com/data", true);
xhr.onreadystatechange = function() {
  if (xhr.readyState === 4 && xhr.status === 200) {
    var response = JSON.parse(xhr.responseText);
    console.log(response);
  }
};
xhr.send();

In this example, we sent a GET request to http://example.com/data via AJAX. If the server allows cross-domain requests, And after returning the response data that meets the requirements, we can process the response in the front-end code.

Conclusion:
AJAX is a powerful technology that has many wonderful features in addition to the common asynchronous loading of data. By dynamically loading CSS style sheets, file upload progress prompts, and cross-domain requests, we can further improve the performance and user experience of web applications. Using AJAX, we can achieve asynchronous communication with the server and dynamically update the page content without reloading the entire page through JavaScript.

Please note: The code examples in this article are for reference only. Please make appropriate modifications and adjustments according to specific needs in actual use.

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