Wie können Sie die Eingabe von HTML-Formularen mit JavaScript validieren?

User experience is key. Format input on the backend and allow user to input form with as little "red alerts" as possible. It will pay off in submission ratio

We should always remember client-side validation is for the benefit of user-friendliness: creating a smooth and reactive UI that allows users to quickly select and enter valid data using the provided interface. Actual comprehensive input validation must always happen server-side, especially considering text inputs, querystrings and valid data ranges. And last, but not least, we have to make sure that any data we collect is stored in such a way as to prevent accidental code execution (encoded, stripped of html and xml tags, etc., database views, procs and functions never use string data to assemble queries, etc.)

In my experience, this validating the input in the frontend layer is quite important. This ensures that we can instantly show the errors to the user.

syntax, a password meets certain security standards, or a date is within a certain range. Form validation can help prevent errors, improve user experience, and enhance security.

I agree that front end validation is not a replacement for back end validation. It is helpful from a user perspective though, which is what I think was intended by the author- that it improves the overall experience and quality of the page. If there is no front end validation- the user will wait for the HTTP request-response cycle to complete, and then rightly be frustrated if it fails. I use HTML5 pattern attributes with RegEx, React and Bootstrap CSS style sheets- storing input in state and include at least two methods to handle change in input and handle submission button. ** You must protect the backend from malicious users who can directly send requests to your server and avoid front end validation altogether.**

Client side validation is not a replacement for back end validation, but it is an excellent compliment. Using JavaScript for validation serves to prevent the backend from using resources to prevent simple mistakes and ensures that back end validation is a safety net for front end code mistakes and security.

Some reasons why JavaScript is commonly utilized for form validation on websites purpose: 1. Real-time validation 2. Client-side validation 3. Immediate user feedback 4. Enhanced user experience 5. Reduced server load 6. Customizability JavaScript provides a powerful and versatile solution for form validation on websites. Its real-time validation, client-side execution, immediate user feedback, and customizable features make it an excellent choice for enhancing user experience and optimizing server performance.

Client-side validation also allows us to validate the form as it is filled out so that data is ready before it is ever submitted.

Validation on the front end isn't going to improve client-side performance. At least I can't think of any reason why it would. If anything, there's going to be some additional cost to implement validation, especially for more complex rules. Ideally though, the front end should perform simple validations like type-checking and character counts, while more complex validations are offloaded to the server. I think the article should specify that validating form data can reduce the workload on the server, so server-side performance is improved. But as far as the client-side performance, I don't that's a true claim. Poorly implemented front-end validation can actually hurt or even break the user experience.

Form elements can also be selected by class name and query selector. document.getElementsByClassName("className") can be used to select form elements with class="className" attribute. You can also select the same elements with querySelectorAll(".className"). querySelector returns the first element that matches the CSS selector and querySelectorAll returns all matching elements.

Form elements can be accessed as a list of elements using the `form.elements` property, where `form` is a reference to the form itself. This has worked in browsers for decades, and is better than methods like getElementsByClassName() or querySelectorAll() as it allows better selection when multiple forms exist on the page at one time.

Apart from what Ashley mentioned, I rarely use min and max attributes for any numerical values. Reason being that it’s highly error prone. Negative value checks needs to be checked in those cases. I prefer either custom Js or either any existing library provided by the framework I’m working with.

Don't validate your form using custom JS code where better built-in validation exists. There is a very capable Form Validation API built in to browsers that handles things like email address & URL validation, character length & number range checks, and even support for regular expression patterns where all else fails. All that without needing a single line of Javascript.

Don't style error or success messages using colour alone. This fails basic accessibility checks. At best, it's a poor experience for your users, at the worst, it can leave a website and its owners open to legal liability.

It would be more efficient to allocate these CSS styles to two distinct classes and switch the class based on the error or success status, rather than setting explicit styles. By doing this, you can conveniently reuse the same classes throughout your application.

HTML also supports form validation. The "required" attribute is used to check that the field is not empty, and the input type is used by the browser to check that the data is correct. In this way, you can check an email address, a URL, a number, a range of values, a color, a date, etc. All this works in all modern browsers. But if you want to customize the error, then you must use JavaScript.

Ideally, form validations should be isomorphic, which means they can run on the server and client. This approach allows reusability, which decreases the time for maintainability. Another important aspect to consider is that validations should be separate from the application's logic, running as standalone modules, so they do not end up getting tangled in the code. There are many isomorphic validation engines for browser client and node apps available for use; it is worth investing time in benchmarks before implementing your validation module.

Efficiently manage form validation with dynamic checks, handle generated inputs seamlessly, and conduct thorough cross-field validation. Employ remote validation for instant user feedback, prioritise data sanitization for security, and use localization for global users. Customise validation for complex interactions, optimise with debounce and throttle, and create unique validation rules. Leverage validation libraries for faster development while testing and refining the user experience.