Home Web Front-end JS Tutorial Detailed example of ajax attribute async in jQuery

Detailed example of ajax attribute async in jQuery

Dec 04, 2017 pm 04:48 PM
ajax async jquery

In our daily development work, ajax is knowledge that we all need to learn. So in jquery's ajax, if we want to achieve synchronization or asynchronousness, we can directly set async occurrence to true or false. It can be true or false. Today we will introduce you to the example of ajaxattributeasync in jQuery!

Example 1, jquery+ajax/" target="_blank">jquery ajax synchronization method

The code is as follows:

$.ajax({
url : 'test.php',
type : 'post',
async: false,//使用同步的方式,true为异步方式
data : {'act':'addvideo', 'videoname':videoname},//这里使用json对象
success : function(data){
//code here...
},
fail:function(){
//code here...
}
});
Copy after login

Example 2

The code is as follows:

//javascript
function test()
{
 var a= 1;
 $.ajax({
  type   : 'GET',
  url    : 'test.php',
  data   : 'page=112',
  success:function(msg)
  {
   alert(msg);
   a= msg;
  }
 })
 alert(a);
}
//test.php
sleef('5'); //休息五分钟
echo 'in';
/*
 这个程序运行情况是  先打印1(a=1) 然后五秒过后 打印 in
 根据这个情况就可以知道 jquery 的ajax的执行流程 
 因为是异步调用
 以前就是这样给一个变量赋值  不管怎么弄都是不对的。最后就发现这个问题
 参数async改为false就为同步调用 当ajax返回结果后程序才继续执行
*/
Copy after login

Here, the default setting value of async is true. In this case, it is an asynchronous method, which means that after ajax sends the request, it is waiting for the server to return. , the front desk will continue to execute the script after the ajax block, and will not execute success until the server returns the correct result. That is to say, two threads are executed at this time, one thread after the ajax block sends the request and the script after the ajax block ( Another thread) Example:
Example 3

The code is as follows:

$.ajax({  
          type:"POST", 
         url:"Venue.aspx?act=init", 
           dataType:"html", 
          success:function(result){   //function1()
             f1(); 
             f2(); 
        } 
         failure:function (result) {  
            alert('Failed');  
         }, 
  } 
  function2();
Copy after login

In the above example, when the ajax block makes a request, he will stay in function1() and wait. The server side returns, but at the same time (during this waiting process), the front desk will execute function2(), that is to say, two threads will appear at this time, let's call them function1() and function2() for now
. When asyn is set to false, the ajax request is synchronous. That is to say, after the ajax block sends a request at this time, it will wait at function1() and will not execute function2() until function1( ) partially executed.

Summary:

Synchronization means that when the JS code is loaded into the current AJAX, the page will be loaded. All the code in it stops loading, and the page goes out of the suspended state. When this AJAX is executed, other codes will continue to run. The suspended state will be released. Async: jquery's async: false can still run while the AJAX code is running. , this attribute

Related recommendations:

async and defer usage in script tags

Detailed explanation of ES6's async+await synchronization/asynchronous solution

Detailed explanation of the usage of async in javascript

The above is the detailed content of Detailed example of ajax attribute async in jQuery. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

PHP and Ajax: Building an autocomplete suggestion engine PHP and Ajax: Building an autocomplete suggestion engine Jun 02, 2024 pm 08:39 PM

Build an autocomplete suggestion engine using PHP and Ajax: Server-side script: handles Ajax requests and returns suggestions (autocomplete.php). Client script: Send Ajax request and display suggestions (autocomplete.js). Practical case: Include script in HTML page and specify search-input element identifier.

How to use PUT request method in jQuery? How to use PUT request method in jQuery? Feb 28, 2024 pm 03:12 PM

How to use PUT request method in jQuery? In jQuery, the method of sending a PUT request is similar to sending other types of requests, but you need to pay attention to some details and parameter settings. PUT requests are typically used to update resources, such as updating data in a database or updating files on the server. The following is a specific code example using the PUT request method in jQuery. First, make sure you include the jQuery library file, then you can send a PUT request via: $.ajax({u

How to get variables from PHP method using Ajax? How to get variables from PHP method using Ajax? Mar 09, 2024 pm 05:36 PM

Using Ajax to obtain variables from PHP methods is a common scenario in web development. Through Ajax, the page can be dynamically obtained without refreshing the data. In this article, we will introduce how to use Ajax to get variables from PHP methods, and provide specific code examples. First, we need to write a PHP file to handle the Ajax request and return the required variables. Here is sample code for a simple PHP file getData.php:

jQuery Tips: Quickly modify the text of all a tags on the page jQuery Tips: Quickly modify the text of all a tags on the page Feb 28, 2024 pm 09:06 PM

Title: jQuery Tips: Quickly modify the text of all a tags on the page In web development, we often need to modify and operate elements on the page. When using jQuery, sometimes you need to modify the text content of all a tags in the page at once, which can save time and energy. The following will introduce how to use jQuery to quickly modify the text of all a tags on the page, and give specific code examples. First, we need to introduce the jQuery library file and ensure that the following code is introduced into the page: &lt

Use jQuery to modify the text content of all a tags Use jQuery to modify the text content of all a tags Feb 28, 2024 pm 05:42 PM

Title: Use jQuery to modify the text content of all a tags. jQuery is a popular JavaScript library that is widely used to handle DOM operations. In web development, we often encounter the need to modify the text content of the link tag (a tag) on ​​the page. This article will explain how to use jQuery to achieve this goal, and provide specific code examples. First, we need to introduce the jQuery library into the page. Add the following code in the HTML file:

PHP vs. Ajax: Solutions for creating dynamically loaded content PHP vs. Ajax: Solutions for creating dynamically loaded content Jun 06, 2024 pm 01:12 PM

Ajax (Asynchronous JavaScript and XML) allows adding dynamic content without reloading the page. Using PHP and Ajax, you can dynamically load a product list: HTML creates a page with a container element, and the Ajax request adds the data to that element after loading it. JavaScript uses Ajax to send a request to the server through XMLHttpRequest to obtain product data in JSON format from the server. PHP uses MySQL to query product data from the database and encode it into JSON format. JavaScript parses the JSON data and displays it in the page container. Clicking the button triggers an Ajax request to load the product list.

Understand the role and application scenarios of eq in jQuery Understand the role and application scenarios of eq in jQuery Feb 28, 2024 pm 01:15 PM

jQuery is a popular JavaScript library that is widely used to handle DOM manipulation and event handling in web pages. In jQuery, the eq() method is used to select elements at a specified index position. The specific usage and application scenarios are as follows. In jQuery, the eq() method selects the element at a specified index position. Index positions start counting from 0, i.e. the index of the first element is 0, the index of the second element is 1, and so on. The syntax of the eq() method is as follows: $("s

PHP and Ajax: Ways to Improve Ajax Security PHP and Ajax: Ways to Improve Ajax Security Jun 01, 2024 am 09:34 AM

In order to improve Ajax security, there are several methods: CSRF protection: generate a token and send it to the client, add it to the server side in the request for verification. XSS protection: Use htmlspecialchars() to filter input to prevent malicious script injection. Content-Security-Policy header: Restrict the loading of malicious resources and specify the sources from which scripts and style sheets are allowed to be loaded. Validate server-side input: Validate input received from Ajax requests to prevent attackers from exploiting input vulnerabilities. Use secure Ajax libraries: Take advantage of automatic CSRF protection modules provided by libraries such as jQuery.

See all articles