This article mainly introduces the method of asynchronous loading of ajax images. It analyzes the principles and related implementation techniques of asynchronous loading of ajax images in detail in the form of examples. Friends in need can refer to the following
Examples of this article Ajax method for asynchronously loading images. I share it with you for your reference. The details are as follows:
Pictures are generally relatively large, so they are loaded gradually after the basic web page is loaded. The whole loading process is very unsightly, or it gradually changes from blurry to blurry. Clear, or expanded from top to bottom (of course you can also think that these are good special effects). If the dynamic replacement of the image is achieved by regularly changing the src attribute of the img, the resulting flicker will be even more unacceptable. This is not something that can be pleasant with the alt attribute.
Contact the popular AJAX technology, which is known as "no" refresh. It uses the XMLHttpRequest object to initiate an asynchronous request. After the image is loaded, it is dynamically inserted into the "foreground" HTML page. It should be able to meet the needs, but the object returned by the XMLHttpRequest object has only two attributes, responseXML and responseText. The former is an XML object, and the latter is the returned plain text content. It seems that there is no binary data required for the picture... Taking a step back, even if it can be used responseText retrieves the binary data of the image, how can we insert it into the front page? Replace the src attribute of img with the requested url?
Just do it and write an image slideshow code to verify your idea:
<html>
<head>
<title>Image Slide</title>
<script>
function makeAsyncRequest(url, callback)
{
var httpRequest;
if (window.XMLHttpRequest) { // Mozilla, Safari, ...
httpRequest = new XMLHttpRequest();
if (httpRequest.overrideMimeType) {
httpRequest.overrideMimeType('text/xml');
}
} else if (window.ActiveXObject) { // IE
try {
httpRequest = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
httpRequest = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e) {
}
}
}
httpRequest.onreadystatechange = function () {
if (httpRequest.readyState == 4
&& httpRequest.status == 200)
callback(url);
};
httpRequest.open('GET', url, true);
httpRequest.send('');
}
var i = 0;
var max_i = 10;
function displayImage()
{
var url = "./" + i + ".jpg";
makeAsyncRequest(url, function (url) {
var p = document.getElementById("image");
var img = p.getElementsByTagName("img");
if (img.length == 0) {
img = document.createElement("img");
while (p.childNodes.length > 0)
p.removeChild(p.childNodes[0]);
p.appendChild(img);
} else
img = img.item(0);
img.src = url;
if (i == max_i)
i = 0;
else
i ++;
window.setTimeout("displayImage();", 1000);
});
}
</script>
</head>
<body onload="displayImage();">
<p id="image">
</p>
</body>
</html>The above code displays pictures 0.jpg - 10.jpg in a loop at a time interval of 1000 milliseconds. The effect is more obvious and flickering is indeed eliminated. So how does it work? The display of each image is divided into two steps:
Use the XMLHttpRequest object to obtain the image from the server, and cache the image to the local browser buffer.
Get the image from the local browser buffer for display.
Because the time from taking the picture to displaying it in the second step is very short, the user basically cannot detect any flicker. It can be seen that the above technology is based on the assumption that the requested image is cacheable. If the image is not cacheable, will the above code not work properly?
Let the code speak for itself and make some changes to the above code:
function displayImage()
{
var url = "./" + i + ".jpg";
var url = "./image.php?filename=" + i + ".jpg";
makeAsyncRequest(url, function (url) {
var p = document.getElementById("image");
var img = p.getElementsByTagName("img");Write another php script to transmit the requested image:
<?php
header("Content-Type: image/jpeg");
header("Cache-Control: no-cache");
echo file_get_contents($_GET["filename"]);
?>As expected , it flickered again...
It seems that we need to think of another way. Working behind closed doors will not work. Please ask Mr. Google for help! The hard work paid off, and I finally found it. I was overjoyed. The result still surprised me. IMG actually has an onload event callback interface. I can only be glad that my glasses are made of resin. "I am not afraid if my glasses fall off." Well, don't be afraid, don't be afraid, don't be afraid..."
What are you waiting for? Of course the code will serve you:
<html>
<head>
<title>Image Slide</title>
<script>
var i = 0;
var max_i = 10;
function displayImage()
{
var img = document.createElement("img");
img.onload = function () {
var p = document.getElementById("image");
while (p.childNodes.length > 0)
p.removeChild(p.childNodes[0]);
p.appendChild(img);
if (i == max_i)
i = 0;
else
i ++;
window.setTimeout("displayImage();", 1000);
}
img.src = "./" + i + ".jpg";
}
</script>
</head>
<body onload="displayImage();">
<p id="image">
</p>
</body>
</html>"She is an ungly girl!"Nothing to say, non-cacheable image Situation:
i ++;
window.setTimeout("displayImage();", 1000);
}
img.src = "./" + i + ".jpg";
img.src = "./image.php?filename=" + i + ".jpg";
}
</script>
</head>The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.
Related articles:
AJAX request queue implementation
Summary of several methods of using ajax to submit forms asynchronously
How to solve the problem of arrays in AJAX requests
The above is the detailed content of Ajax asynchronous loading image example analysis. For more information, please follow other related articles on the PHP Chinese website!
Javascript Data Types : Is there any difference between Browser and NodeJs?May 14, 2025 am 12:15 AMJavaScript core data types are consistent in browsers and Node.js, but are handled differently from the extra types. 1) The global object is window in the browser and global in Node.js. 2) Node.js' unique Buffer object, used to process binary data. 3) There are also differences in performance and time processing, and the code needs to be adjusted according to the environment.
JavaScript Comments: A Guide to Using // and /* */May 13, 2025 pm 03:49 PMJavaScriptusestwotypesofcomments:single-line(//)andmulti-line(//).1)Use//forquicknotesorsingle-lineexplanations.2)Use//forlongerexplanationsorcommentingoutblocksofcode.Commentsshouldexplainthe'why',notthe'what',andbeplacedabovetherelevantcodeforclari
Python vs. JavaScript: A Comparative Analysis for DevelopersMay 09, 2025 am 12:22 AMThe main difference between Python and JavaScript is the type system and application scenarios. 1. Python uses dynamic types, suitable for scientific computing and data analysis. 2. JavaScript adopts weak types and is widely used in front-end and full-stack development. The two have their own advantages in asynchronous programming and performance optimization, and should be decided according to project requirements when choosing.
Python vs. JavaScript: Choosing the Right Tool for the JobMay 08, 2025 am 12:10 AMWhether to choose Python or JavaScript depends on the project type: 1) Choose Python for data science and automation tasks; 2) Choose JavaScript for front-end and full-stack development. Python is favored for its powerful library in data processing and automation, while JavaScript is indispensable for its advantages in web interaction and full-stack development.
Python and JavaScript: Understanding the Strengths of EachMay 06, 2025 am 12:15 AMPython and JavaScript each have their own advantages, and the choice depends on project needs and personal preferences. 1. Python is easy to learn, with concise syntax, suitable for data science and back-end development, but has a slow execution speed. 2. JavaScript is everywhere in front-end development and has strong asynchronous programming capabilities. Node.js makes it suitable for full-stack development, but the syntax may be complex and error-prone.
JavaScript's Core: Is It Built on C or C ?May 05, 2025 am 12:07 AMJavaScriptisnotbuiltonCorC ;it'saninterpretedlanguagethatrunsonenginesoftenwritteninC .1)JavaScriptwasdesignedasalightweight,interpretedlanguageforwebbrowsers.2)EnginesevolvedfromsimpleinterpreterstoJITcompilers,typicallyinC ,improvingperformance.
JavaScript Applications: From Front-End to Back-EndMay 04, 2025 am 12:12 AMJavaScript can be used for front-end and back-end development. The front-end enhances the user experience through DOM operations, and the back-end handles server tasks through Node.js. 1. Front-end example: Change the content of the web page text. 2. Backend example: Create a Node.js server.
Python vs. JavaScript: Which Language Should You Learn?May 03, 2025 am 12:10 AMChoosing Python or JavaScript should be based on career development, learning curve and ecosystem: 1) Career development: Python is suitable for data science and back-end development, while JavaScript is suitable for front-end and full-stack development. 2) Learning curve: Python syntax is concise and suitable for beginners; JavaScript syntax is flexible. 3) Ecosystem: Python has rich scientific computing libraries, and JavaScript has a powerful front-end framework.
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
SecLists
SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.
MantisBT
Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.
ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment
SublimeText3 Chinese version
Chinese version, very easy to use
