Send synchronous request in jquery

With the continuous development of front-end technology, Ajax has become an indispensable part of our daily development. As one of the most popular tool libraries in the front-end world, jQuery also provides a wealth of Ajax-related APIs. Among them, the jQuery.ajax() method is one of the most commonly used methods. It can be used to send asynchronous requests and process return data. However, in some scenarios, we may need to send synchronous requests. Well, this article will introduce how to send synchronous requests in jQuery.

1. Synchronous requests and asynchronous requests

Before we start to introduce how to send synchronous requests in jQuery, we need to first understand the concepts of asynchronous requests and synchronous requests.

Asynchronous request: Asynchronous request refers to a request method in which the browser does not wait for the server to respond after the request and continues to execute subsequent scripts. In other words, an asynchronous request can be said to be a "non-blocking request" because it will not have much impact on the user interface.

Synchronous request: Synchronous request refers to the request method in which the browser needs to wait for the server response after the request before continuing to execute subsequent scripts. Compared with asynchronous requests, synchronous requests will block the execution of the user interface and bring a bad interactive experience to the user, so it is generally not recommended.

2. Method of sending synchronous requests

In jQuery, we can use the $.ajaxSetup() method to set the default Ajax request options to implement synchronous requests. The specific implementation steps are as follows:

1. First, we need to set the async option of the $.ajaxSetup() method to false, that is, change the asynchronous request to a synchronous request.

$.ajaxSetup({
async: false
});

2. Then, we can use the $.ajax() method to send a synchronous request , its usage is the same as asynchronous request. The following is a simple synchronous request example:

$.ajax({
url: 'test.php', // Backend interface address
type: 'POST', / / Request method
data: {

name: '张三',
age: 20

}, // Request parameters
success: function (res) {

console.log(res);

}, // Success callback function
error : function (xhr, textStatus, errorThrown) {

console.log(textStatus);

} // Failure callback function
});

In the above code, url represents the backend interface address, and type represents the request method, data represents the request parameters, success represents the success callback function, and error represents the failure callback function. For specific usage, please refer to the jQuery official documentation. It should be noted that when sending a synchronous request, because the async option of the ajaxSetup() method is set to false, the request will prevent the browser from executing subsequent scripts until the request is completed.

3. Precautions

Although sending synchronous requests is necessary in some special scenarios, it often prevents the execution of subsequent scripts, causing the page to freeze or other problems. Therefore, we need to pay attention to the following points:

1. Synchronous requests will block the execution of the browser, and should be avoided if necessary.
2. When sending a synchronous request, be sure that the requested backend interface can respond quickly, otherwise the user may wait for a long time.
3. If you must use synchronous requests, it is recommended to add the "Loading" effect before the request to improve user experience.

4. Summary

This article introduces the method of sending synchronous requests in jQuery, and reminds everyone of the details that need to be paid attention to when using synchronous requests. It needs to be emphasized that in most scenarios, asynchronous requests can already meet our needs and avoid problems such as page freezes. Therefore, in project development, we should use asynchronous requests as much as possible and reduce the frequency of synchronous requests.

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