How to achieve synchronization in jquery

jQuery is a very popular JavaScript library that is widely used in front-end development. It provides developers with many convenient methods and functions, one of which is the synchronous method. In this article, we will introduce how jQuery implements synchronization.

What is synchronization?

In JavaScript, synchronization refers to the process of starting the next task only after the previous task is completed. Simply put, synchronization is the execution of code in sequence.

Why synchronization is needed?

Consider this scenario: a web page contains two JavaScript files, one of which downloads faster and the other downloads slower. If the browser encounters a faster file, it will be downloaded first, but since the JavaScript language is single-threaded, it will stop executing the downloaded code until another file is also downloaded. If a slower file takes a long time to download, the entire web page will be stuck and the user experience will be very poor. This is exactly what synchronization needs to solve.

How to achieve synchronization?

When using jQuery, we can achieve synchronization through the $.ajax() function.

$.ajax() is the AJAX function in jQuery, which can implement asynchronous and synchronous AJAX requests. By default, $.ajax() uses an asynchronous method to send AJAX requests, that is, the code continues execution without waiting for a response. But if we set the async attribute to false, we can send the request synchronously, so that the code will not execute the next step until the response is returned.

The following is an example of using $.ajax() to achieve synchronization:

$.ajax({
    url: 'http://example.com/api/getData',
    type: 'GET',
    dataType: 'json',
    async: false, // 将async设置为false，即可实现同步操作
    success: function(response) {
        console.log(response);
    },
    error: function(error) {
        console.log(error);
    }
});

When the async attribute is set to false, the request will be blocked until the server returns a response. This can ensure the order of code execution, but it also has some disadvantages. First, synchronous requests hang the browser until a response comes back from the server, preventing the user from interacting with the page. Secondly, synchronous requests will block the execution of JavaScript code. If the server response time is very slow, the web page will look very stuck.

Summary

In actual development, we should try to avoid synchronization operations because it will block the JavaScript thread and reduce the user experience. If you must use synchronous requests, please pay attention to the response time and blocking time to avoid unnecessary waiting and anxiety for users.

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