Скачать или смотреть How to Select Items by Pseudo Class Using jQuery

Discover how to rewrite vanilla JavaScript for selecting invalid form fields using jQuery with easy-to-understand examples.
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This video is based on the question https://stackoverflow.com/q/64987956/ asked by the user 'Lelio Faieta' ( https://stackoverflow.com/u/2399035/ ) and on the answer https://stackoverflow.com/a/64987998/ provided by the user 'Jamiec' ( https://stackoverflow.com/u/219661/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Selecting Items by Pseudo Class Using jQuery

Working with HTML forms can pose various challenges, especially when it comes to styling and validating form elements. One common task is selecting elements based on their validation state, such as identifying which fields are invalid. In this guide, we will explore how to effectively select items using pseudo-classes in jQuery, specifically focusing on the :invalid pseudo-class.

The Problem

You may have a form with an ID — let's call it myform — and you want to apply custom styling for invalid fields. In vanilla JavaScript, you would typically use the querySelectorAll method to target these elements like this:

[[See Video to Reveal this Text or Code Snippet]]

Where form is your form element. However, if you're working in an environment that utilizes jQuery, you may wonder how to replicate this functionality using jQuery syntax.

The Solution

Fortunately, jQuery provides a straightforward way to select elements based on their validation state. Instead of using querySelectorAll, you can leverage jQuery’s selector capabilities. The equivalent jQuery code for selecting the :invalid pseudo-class is:

[[See Video to Reveal this Text or Code Snippet]]

Step-by-Step Example

Let’s take a look at a complete example to illustrate how this works in practice.

HTML Structure

First, create a simple HTML form with some required fields:

[[See Video to Reveal this Text or Code Snippet]]

JavaScript Functionality

Next, implement the jQuery functionality to identify invalid fields when the button is clicked. This approach uses the :invalid selector within jQuery and processes the fields:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

Button Click Event: The code begins by attaching an event handler to a button click with $('button').on("click", ...).

Form Selection: The form is selected by its ID using $('# myform').

Invalid Fields Selection: The :invalid pseudo-class is used to find all invalid fields within the selected form, providing a jQuery set of elements.

Iterating through Invalid Fields: Finally, we use .each() to iterate over the invalid fields and log their id to the console for visibility.

Conclusion

In conclusion, selecting items by pseudo-class using jQuery can simplify the management of form validation. By employing the :invalid selector, you can effectively identify and style the fields that do not meet the criteria set by HTML5, creating more responsive and user-friendly forms.

With the examples provided, you should be able to implement jQuery's selection of invalid fields in your projects seamlessly.

Happy coding!