Why jquery has no effect

In daily front-end development, we often need to use jQuery to operate DOM, achieve dynamic effects, etc. However, sometimes we encounter situations where jQuery is invalid. What should we do at this time?

1. Check whether jQuery is imported correctly

First, we need to ensure that jQuery is imported correctly. You can check whether a "$ is not defined" error occurs by typing $ in the console. If this error occurs, it means jQuery has not been introduced correctly. At this time, you need to check whether the import path is correct, whether the file exists, etc.

2. Confirm whether the jQuery version is consistent

When we introduce multiple jQuery versions at the same time, jQuery may become invalid. At this time, you need to check whether the jQuery versions between each module are consistent. You can check the jQuery version number referenced by the current page by entering $.fn.jquery in the console to confirm whether the versions are consistent.

3. Check whether the DOM is loaded

In jQuery, a common problem is that the jQuery code is executed before the DOM is loaded. If jQuery code is executed when the DOM is not loaded, the jQuery selector cannot find the corresponding element, resulting in invalidity. At this time, you can use $(document).ready() or $(function(){}) to ensure that the DOM is loaded before executing the jQuery code.

4. Confirm whether the selector is correct

When we use jQuery, the selector may not be able to select an element. At this point you need to double check that the selector is correct. You can check whether the target element is selected by entering the jQuery selector in the console. If the selector is correct but you still can't select the element, there may be another problem.

5. Check whether the code logic is correct

In jQuery, sometimes we need to write complex logic to achieve certain functions. When there is a problem with the code logic, it may also cause jQuery to be invalid. At this time, you need to check whether the code logic is correct and whether there will be problems such as infinite loops and loose logic.

6. Confirm whether the CSS style is correct

Sometimes we use jQuery to achieve style effects, but it is invalid. At this time, you need to check whether the CSS style is correct. For example, when using the animate() method, you need to ensure that the CSS properties are set correctly.

Summary

When developing with jQuery, invalid situations are often encountered. We need to carefully analyze the problem and investigate step by step to find the problem and solve it. At the same time, when writing code, you must also follow jQuery's syntax specifications to ensure the readability and maintainability of the code, thereby avoiding invalid situations.

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