How to use jquery

How to use jquery: First load the jquery file through CDN loading or local loading of files; then execute the jQuery code through the jquery file.

The operating environment of this article: Windows 7 system, Dell G3 computer, jquery version 3.2.1.

How to use jquery? This article will introduce to you what is jquery? Why use jquery? How to use jquery? Let everyone know how to use jquery, I hope it will be helpful to you.

What is jQuery?

jQuery is not a language, but it is well-written JavaScript code. It is a fast and concise JavaScript library that simplifies HTML document traversal, event handling, animation and Ajax Interactive for rapid web development.

Why choose jQuery?

jQuery is a very compact and well-written JavaScript code that improves developer productivity by writing very small amounts of code so that they can implement critical UI functionality.

The advantages of jQuery are:

1. There is no need to learn a new syntax to use jQuery, it is enough to understand simple JavaScript syntax.

2. The code is simple and clear, and complex functions can be implemented without writing multiple lines of code.

3. Helps improve application performance.

4. It helps develop web pages that are compatible with most browsers.

5. It helps to implement key UI-related functions without writing hundreds of lines of code.

How to use jQuery?

#1. Load the jQuery file

jQuery usually comes as a single JavaScript file that contains everything jQuery does out of the box. It can be included in a web page in the following ways:

1), load local jQuery file

First you need to

download the jQuery file to the local, jQuery JavaScript files can be downloaded from the jQuery official website, address: http://www.jquery.com.

Then load jQuery files

<script type="text/javascript" src="jQuery-1.4.1-min.js"></script>

2), load jQuery from CDN

What is CDN?

CDN stands for Content Distribution Network, also known as Content Delivery Network. It is a group of computers placed at various points connected to the replica network containing data files to maximize bandwidth. In a CDN, clients access a copy of the data closer to the client's location, rather than all clients accessing it from one specific server. This helps achieve better data retrieval performance on the client side.

There are two main CDNs available for hosting jQuery files:

a. Loading jQuery from the Microsoft AJAX CDN

Can be loaded from Microsoft AJAX CDN loads jQuery files. More details are available here. You need to keep the following markup in your page.

<script type="text/javascript" language="Javascript"  src="http://ajax.aspnetcdn.com/ajax/jquery/jquery-1.4.1.min.js"></script>

b. Loading jQuery from Google Libraries API

You can load jQuery files from Google CDN. You need to keep the following markup in your page.

<script type="text/javascript" language="Javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.4.4/jquery.min.js"> </script>

Benefits of loading jQuery from CDN:

1. Since there is no need to download the jQuery file, the page loads faster

2. Load jQuery files from the server, thus saving bandwidth

3. Scalable, usually CDNs place these files on servers located in different geographical locations around the world so that they load faster, so no matter where the user is browsing page, and your application will run normally.

Note:

Generally, loading jQuery from CDN and loading jQuery files from local area must be written in order to prevent loading jQuery files. CDN is not available. Therefore, you can write the following lines of code:

<!-- START - jQuery Reference -->
<script type="text/javascript" language="Javascript" 

    src="http://ajax.aspnetcdn.com/ajax/jquery/jquery-1.4.1.min.js"></script>
    <script type=&#39;text/javascript&#39;>//<![CDATA[
        if (typeof jQuery == &#39;undefined&#39;) {
            document.write(unescape("%3Cscript 
    src=&#39;/Script/jquery-1.4.1.min.js&#39; type=&#39;text/javascript&#39; %3E%3C/script%3E"));
}//]]>
</script>
<!-- END - jQuery Reference -->

2. Execute jQuery code

We may have two ways to execute jQuery code.

1. When the page loads, execute the jQuery code:

<script language="javascript" type="text/javascript">
$(function () {
$("#div1").css("border", "2px solid green");
});
</script>

or:

<script language="javascript" type="text/javascript">
$("#div1").css("border", "2px solid green");
</script>

The advantage of executing jQuery code in this way is that it will not wait The entire page loads completely, so you can use this if you want the user to see the effect as soon as the corresponding element loads.

But the disadvantage is that if the element that jQuery has to execute is not loaded, then it will error or you will not get the desired result; therefore, when using this way of executing jQuery code, you must make sure first Load the element where you want to use jQuery (you can put the jQuery code after the HTML element).

2. Only execute jQuery when the complete DOM object (complete page has been loaded). At this point the code must be wrapped in a .ready function.

<script language="javascript" type="text/javascript">
$(document).ready(function () {
$("#div1").css("border", "2px solid green");
});
</script>

这是执行jQuery的更好，更安全的方法。这样可以确保只有在浏览器中加载完整页面时才会执行jQuery代码，因此可以放心，用户不会在页面上看到任何不需要的行为。

总结：以上就是本篇文章的全部内容，希望能对大家的学习有所帮助。

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