javascript - ajax asynchronous problem
Excuse me, is the callback function in ajax
return data and then execute the code in the function
or directly execute the code
in the function without waiting for data to be returned?
If it is the second case, how to avoid the trouble caused by asynchronous?
Reply content:
Excuse me, is the callback function in ajax
return data and then execute the code in the function
or directly execute the code
in the function without waiting for data to be returned?
If it is the second case, how to avoid the trouble caused by asynchronous?
The callback function of success is a function to be executed after the data returns successfully, which means that it will be executed after getting the data.
Other situations include beforeSend (before sending), complete (after the request is completed), error (request error) ) callback
As for the trouble you mentioned caused by asynchronousness, I don’t quite understand it. Can you give me an example?
You must return data and then execute the code in the function = = Execute without returning data = = Isn’t it waiting for an error?
The full name of
ajax
AJAX = Asynchronous JavaScript and XML
(asynchronous JavaScript and XML).
To answer your question first, in the case of success, the function will not be executed until data is successfully returned. If there is no return, it will wait for a while. This time is usually the network delay time. You can also set it yourself.
The following is a brief introduction to the ajax
of the great jquery
framework.
Usually, I use it like this, in the form of name+value.
<code>$.ajax({name:value, name:value, ... })</code>
async
Boolean value indicating whether the request is processed asynchronously. The default is true. Set to false, you will turn off asynchrony. At this time, one request will cause the interface to be very stuck.beforeSend(xhr)
Function that runs before sending a request.cache Boolean value indicating whether the browser caches the requested page. The default is true.
complete(xhr,status)
Function that runs when the request is completed (called after the request succeeds or fails, that is, after the success and error functions).contentType The content type used when sending data to the server. The default is: "application/x-www-form-urlencoded".
context specifies the "this" value for all AJAX related callback functions.
data
Specifies the data to be sent to the server.dataFilter(data,type) Function used to process XMLHttpRequest raw response data.
dataType
The expected data type of the server response.error(xhr, status, error)
Function to run if the request fails.global Boolean value that specifies whether the global AJAX event handler is triggered for the request. The default is true.
ifModified Boolean value that specifies whether the request will succeed only if the response has changed since the last request. The default is false.
jsonp rewrites the string of the callback function in a jsonp.
jsonpCallback specifies the name of the callback function in a jsonp.
password specifies the password used in HTTP access authentication requests.
processData Boolean value that specifies whether the data sent through the request is converted to a query string. The default is true.
scriptCharset specifies the requested character set.
success(result,status,xhr)
Function that runs when the request is successful.timeout
Set the local request timeout (in milliseconds).traditional Boolean value, specifies whether to use the traditional style of parameter serialization.
type
Specifies the type of request (GET or POST).url
Specifies the URL to send the request. The default is the current page.username specifies the username used in HTTP access authentication requests. This can simulate user login, plus password, you know.
xhr Function used to create XMLHttpRequest objects.
The red part is what I commonly use.
Call back this success function after the interface you requested successfully responds with data, so as long as your server handles it normally, the data returned is the data you want
The answer to the question has been mentioned above, so I won’t repeat it. I just want to ask you about the problems of asynchronousness.

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

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)

Hot Topics

PHP 8.4 brings several new features, security improvements, and performance improvements with healthy amounts of feature deprecations and removals. This guide explains how to install PHP 8.4 or upgrade to PHP 8.4 on Ubuntu, Debian, or their derivati

If you are an experienced PHP developer, you might have the feeling that you’ve been there and done that already.You have developed a significant number of applications, debugged millions of lines of code, and tweaked a bunch of scripts to achieve op

Visual Studio Code, also known as VS Code, is a free source code editor — or integrated development environment (IDE) — available for all major operating systems. With a large collection of extensions for many programming languages, VS Code can be c

JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,

This tutorial demonstrates how to efficiently process XML documents using PHP. XML (eXtensible Markup Language) is a versatile text-based markup language designed for both human readability and machine parsing. It's commonly used for data storage an

A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total

Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.

What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.
