What should I do if it prompts that jquery is not defined?

With the continuous development and popularization of front-end technology, more and more websites and applications begin to rely on the jQuery library. However, sometimes you encounter a common problem when using jQuery - jquery is not defined. When this problem occurs, all code on the page that uses jQuery stops working properly. This article will introduce how to solve the problem that jquery is not defined.

1. Confirm whether jQuery is introduced correctly

When jQuery is introduced into the page in an incorrect way or the jQuery file is missing, the problem that jquery is not defined will occur. In this case, we need to check the following points:

• Confirm whether the jQuery file is imported correctly. You can check whether the imported js file is loaded successfully through the Network tab of the browser developer tools.
• Confirm whether the jQuery file path is correct. If the jQuery file path is wrong, the browser will prompt a 404 error, indicating that the file is not found.

2. Introducing jQuery using CDN

CDN is a technology that distributes data over the network, which can improve the access speed and availability of websites and applications. Many websites and applications use CDN to introduce jQuery because CDN is usually characterized by high speed and stability. When there is a problem with the jQuery file imported locally, you can try to use a CDN to import jQuery.

The following is a commonly used sample code for CDN to introduce jQuery:

<script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.min.js"></script>

Note that when using CDN to introduce jQuery, you need to ensure that the network is smooth, otherwise the loading speed may be slow or the loading may fail. question.

3. Confirm the code execution order

When using jQuery, there may be cases where the code execution order is incorrect. If jQuery has not been loaded or executed when executing code that uses jQuery, a jquery not defined error will occur. To avoid this situation, we can take the following measures:

• Place jQuery code before the code that uses jQuery.
• Wait until jQuery is fully loaded and executed before executing the relevant code. You can use jQuery's $(document).ready() method to ensure that you wait for jQuery to fully load and execute.

4. Confirm the jQuery version number

When using jQuery, the version number may also cause the problem that jquery is not defined. This problem will occur if the imported jQuery version does not match. In order to solve this problem, we need to do the following two things:

• Confirm the jQuery version that the code depends on.
• Confirm that the jQuery version we introduced is consistent with the jQuery version the code depends on.

5. Use the noConflict() method

When using jQuery, it may conflict with other libraries or frameworks, resulting in jQuery not being defined. To solve this problem, we can use jQuery's noConflict() method to avoid conflicts.

After using the noConflict() method, we need to use a variable to store jQuery, and then use this variable to call jQuery. The following is a sample code using the noConflict() method:

<script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.min.js"></script>
<script>
  var $j = $.noConflict();
  //使用$j来调用jQuery代码
</script>

Summary

When using jQuery, sometimes you will encounter the problem that jquery is not defined. If we can carefully check whether jQuery is correctly introduced, use CDN to introduce it, confirm the code execution sequence, confirm the jQuery version number, and use the noConflict() method, we can quickly solve the problem of jQuery not being defined.

The above is the detailed content of What should I do if it prompts that jquery is not defined?. For more information, please follow other related articles on the PHP Chinese website!