Learn more about the functions and features of Ajax-JS Tutorial-php.cn

Learn more about the functions and features of Ajax

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Release： 2024-01-30 10:54:06

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Learn more about the functions and features of Ajax

In-depth understanding of Ajax: Function overview, specific code examples are required

Introduction:

In today's Internet era, users have more and more requirements for web pages High, hope that the page can respond and interact with the server in real time. In order to meet this demand, Ajax (Asynchronous JavaScript and XML) is widely used in Web development because of its asynchronous characteristics. This article will delve into the capabilities of Ajax and provide specific code examples.

1. Basic concepts and principles of Ajax

Ajax is a technology that communicates asynchronously with the server without refreshing the entire page. It is mainly implemented based on the following core principles:

Use the XMLHttpRequest object to exchange data with the server in the background, which means that part of the page content can be updated without refreshing the page.
Use JavaScript and DOM to realize dynamic display of the page, and render the data returned by the server to the page in real time.
Use the ability of asynchronous requests to realize data interaction with the server, allowing users to interact with the server through form submission, search, etc.

2. The main functions of Ajax

Asynchronous loading of data

Ajax can load data and display it in real time by sending asynchronous requests to the server on the page without refreshing the entire page. This can greatly improve the page loading speed in terms of user experience and reduce the burden on the server.

Dynamic update of page content

Through Ajax, partial refresh of the page can be achieved, and the data returned by the server can be rendered on the page in real time. In this way, users can obtain the latest content without refreshing the page, improving the interactive experience.

Form submission and verification

Asynchronous form submission can be achieved through Ajax without refreshing the entire page, allowing users to submit data to the server through Ajax after entering data in the form Perform verification, obtain verification results and display them to the user in real time.

Real-time search

Ajax can send a request to the server in real time while the user enters the keyword, and update the search result list in real time based on the results returned by the server, so that the user can search The required information can be obtained more quickly during the process.

3. Code Example

The following is a simple code example to demonstrate the basic usage of Ajax. In this example, we obtain the search results from the server through Ajax based on the keywords entered by the user, and display them on the page in real time.

HTML part:

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Ajax搜索示例</title>
</head>
<body>
    <input type="text" id="keyword" placeholder="请输入关键字">
    <ul id="result"></ul>

    <script src="ajax.js"></script>
</body>
</html>

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JavaScript part:

// ajax.js
document.getElementById("keyword").addEventListener("input", function () {
    var keyword = this.value;
    var xhr = new XMLHttpRequest();
    xhr.open("GET", "search.php?keyword=" + keyword, true);
    xhr.onreadystatechange = function () {
        if (xhr.readyState == XMLHttpRequest.DONE && xhr.status == 200) {
            var result = JSON.parse(xhr.responseText);
            var list = document.getElementById("result");
            list.innerHTML = "";
            result.forEach(function (item) {
                var li = document.createElement("li");
                li.textContent = item;
                list.appendChild(li);
            });
        }
    };
    xhr.send();
});

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PHP part (search.php):

<?php
$keyword = $_GET["keyword"];
$result = array("结果1", "结果2", "结果3");
echo json_encode($result);
?>

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In this example, when the user is on the page When you enter a keyword on the page, the JavaScript code will send a request to the server through Ajax, and render the results returned by the server to the ul element on the page in real time.

Conclusion:

Through the introduction of this article, we can understand the importance of Ajax in Web development and its main functions. By properly applying Ajax technology, we can achieve real-time page updates, asynchronous data interaction, and improve user experience. I hope the code examples in this article can help you better understand and apply Ajax.

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