jQuery ajax() function is the lowest level of abstraction
ThejQuery ajax() function is the lowest level of abstraction available for XMLHttpRequest (aka AJAX). All other jQuery AJAX functions (such as load()) leverage the ajax() function. Using the ajax() function provides the most powerful functionality for XMLHttpRequests. jQuery also provides other higher-level abstractions to perform very specific types of XMLHttpRequests. These functions are essentially shortcuts to the ajax() method.
These shortcuts are:
load()<code>get()<code>getJSON()<code>getScript()<code>post()
It's important to note that while shortcuts are sometimes nice, they all use ajax() behind the scenes. And, when you need all the features and customizations that jQuery offers in terms of AJAX, you should use the ajax() method.
Note: By default, both the ajax() and load() AJAX functions use the GET HTTP protocol.
jQuery supports cross-domain JSONP
JSON with padding (JSONP) is a technology that allows the sender of an HTTP request (which returns JSON) to provide a name for a function that is called with a JSON object as a function argument. This technology does not use XHR. It uses script elements so data can be pulled from any site into any site. The purpose is to circumvent the same-origin policy restrictions of XMLHttpRequest.
Using the <code>getJSON() jQuery function, you can load JSON data from another domain when adding a JSONP callback function to the URL. As an example, here's what a URL request looks like using the Flickr API.
<span class="sgc-100">http://api.flickr.com/services/feeds/photos_public.gne?tags=resig&tagmode=all&format=json&jsoncallback</span>=?
The
? value is used as a shortcut to tell jQuery to call the function passed as an argument to the <code>getJSON() function. If you don't want to use this shortcut, you can replace ? with the name of another function.
Below, I use the Flickr JSONP API to pull in a web page that contains the latest photos tagged with "resig". Note that I'm using the ? shortcut, so jQuery will simply call the callback function of the <code>getJSON() function I provided. The parameter passed to the callback function is the requested JSON data.
<!DOCTYPE html>
<html lang="en">
<body>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
<script> (function($){
$.getJSON("http://api.flickr.com/services/feeds/photos_public.gne?tags=resig&tagmode=all&format=json&jsoncallback=?",
// Using ? just means call the callback function provided
function (data) { // Data is the JSON object from Flickr
$.each(data.items, function (i, item) { $('<img />').attr("src", item.media.m).appendTo('body'); if (i == 30) return false; });
});
})(jQuery); </script>
</body>
</html>
Note: Please make sure to check the API of the service you are using to use callbacks correctly. For example, Flickr uses the name jsoncallback=?, while Yahoo! and Digg use the name callback=?.
Stop browser caching XHR requests
When performing an XHR request, Internet Explorer will cache the response. Caching can be a good thing if the response contains static content with a long shelf life. However, if the content of the request is dynamic and may change at any time, you will need to ensure that the browser does not cache the request. One possible solution is to append a unique query string value to the end of the URL. This will ensure that the browser requests a unique URL for each request.
// Add unique query string at end of the URL url: 'some?nocache='+(newDate()).getTime()
Another solution (more of a global solution) is to default all AJAX requests to include the no-cache logic we just discussed. To do this, turn off caching globally using the ajaxSetup function.
$.ajaxSetup({
cache: false // True by default. False means caching is off.
});
Now, in order to override this global setting with a separate XHR request, you just need to change the cache options when using the ajax() function. Below is a code example that performs an XHR request using the ajax() function, which overrides global settings and caches the request.
$.ajaxSetup ({
cache: false // True by default. False means caching is off.
});
jQuery.ajax({ cache: true, url: 'some', type: 'POST' } );
The above is the detailed content of jQuery Simplified Guide: Exploring jQuery and Ajax. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
How to diagnose high CPU usage caused by WordPress
Jul 06, 2025 am 12:08 AM
The main reasons why WordPress causes the surge in server CPU usage include plug-in problems, inefficient database query, poor quality of theme code, or surge in traffic. 1. First, confirm whether it is a high load caused by WordPress through top, htop or control panel tools; 2. Enter troubleshooting mode to gradually enable plug-ins to troubleshoot performance bottlenecks, use QueryMonitor to analyze the plug-in execution and delete or replace inefficient plug-ins; 3. Install cache plug-ins, clean up redundant data, analyze slow query logs to optimize the database; 4. Check whether the topic has problems such as overloading content, complex queries, or lack of caching mechanisms. It is recommended to use standard topic tests to compare and optimize the code logic. Follow the above steps to check and solve the location and solve the problem one by one.
How to minify JavaScript files in WordPress
Jul 07, 2025 am 01:11 AM
Miniving JavaScript files can improve WordPress website loading speed by removing blanks, comments, and useless code. 1. Use cache plug-ins that support merge compression, such as W3TotalCache, enable and select compression mode in the "Minify" option; 2. Use a dedicated compression plug-in such as FastVelocityMinify to provide more granular control; 3. Manually compress JS files and upload them through FTP, suitable for users familiar with development tools. Note that some themes or plug-in scripts may conflict with the compression function, and you need to thoroughly test the website functions after activation.
How to optimize WordPress without plugins
Jul 05, 2025 am 12:01 AM
Methods to optimize WordPress sites that do not rely on plug-ins include: 1. Use lightweight themes, such as Astra or GeneratePress, to avoid pile-up themes; 2. Manually compress and merge CSS and JS files to reduce HTTP requests; 3. Optimize images before uploading, use WebP format and control file size; 4. Configure.htaccess to enable browser cache, and connect to CDN to improve static resource loading speed; 5. Limit article revisions and regularly clean database redundant data.
How to use the Transients API for caching
Jul 05, 2025 am 12:05 AM
TransientsAPI is a built-in tool in WordPress for temporarily storing automatic expiration data. Its core functions are set_transient, get_transient and delete_transient. Compared with OptionsAPI, transients supports setting time of survival (TTL), which is suitable for scenarios such as cache API request results and complex computing data. When using it, you need to pay attention to the uniqueness of key naming and namespace, cache "lazy deletion" mechanism, and the issue that may not last in the object cache environment. Typical application scenarios include reducing external request frequency, controlling code execution rhythm, and improving page loading performance.
How to prevent comment spam programmatically
Jul 08, 2025 am 12:04 AM
The most effective way to prevent comment spam is to automatically identify and intercept it through programmatic means. 1. Use verification code mechanisms (such as Googler CAPTCHA or hCaptcha) to effectively distinguish between humans and robots, especially suitable for public websites; 2. Set hidden fields (Honeypot technology), and use robots to automatically fill in features to identify spam comments without affecting user experience; 3. Check the blacklist of comment content keywords, filter spam information through sensitive word matching, and pay attention to avoid misjudgment; 4. Judge the frequency and source IP of comments, limit the number of submissions per unit time and establish a blacklist; 5. Use third-party anti-spam services (such as Akismet, Cloudflare) to improve identification accuracy. Can be based on the website
How to enqueue assets for a Gutenberg block
Jul 09, 2025 am 12:14 AM
When developing Gutenberg blocks, the correct method of enqueue assets includes: 1. Use register_block_type to specify the paths of editor_script, editor_style and style; 2. Register resources through wp_register_script and wp_register_style in functions.php or plug-in, and set the correct dependencies and versions; 3. Configure the build tool to output the appropriate module format and ensure that the path is consistent; 4. Control the loading logic of the front-end style through add_theme_support or enqueue_block_assets to ensure that the loading logic of the front-end style is ensured.
How to add custom fields to users
Jul 06, 2025 am 12:18 AM
To add custom user fields, you need to select the extension method according to the platform and pay attention to data verification and permission control. Common practices include: 1. Use additional tables or key-value pairs of the database to store information; 2. Add input boxes to the front end and integrate with the back end; 3. Constrain format checks and access permissions for sensitive data; 4. Update interfaces and templates to support new field display and editing, while taking into account mobile adaptation and user experience.
How to optimize WordPress robots txt
Jul 13, 2025 am 12:37 AM
robots.txt is crucial to the SEO of WordPress websites, and can guide search engines to crawl behavior, avoid duplicate content and improve efficiency. 1. Block system paths such as /wp-admin/ and /wp-includes/, but avoid accidentally blocking the /uploads/ directory; 2. Add Sitemap paths such as Sitemap: https://yourdomain.com/sitemap.xml to help search engines quickly discover site maps; 3. Limit /page/ and URLs with parameters to reduce crawler waste, but be careful not to block important archive pages; 4. Avoid common mistakes such as accidentally blocking the entire site, cache plug-in affecting updates, and ignoring the matching of mobile terminals and subdomains.
