Form verification can be achieved through HTML5 built-in attributes, CSS feedback, JavaScript control and prompt optimization. 1. Use required, type, min, max, pattern and other properties to achieve basic verification; 2. Use the :valid and :invalid pseudo-classes to cooperate with CSS to improve user feedback; 3. Use JavaScript to achieve flexible control through checkValidity() and setCustomValidity() methods; 4. Optimize prompt information and consider old browser compatibility. Front-end verification needs to be combined with back-end verification to ensure data accuracy.
Form verification is an indispensable part of web development. It can effectively ensure that the data entered by users meet expectations and improve user experience and data accuracy. HTML5 provides a series of built-in verification functions, which can achieve basic form verification without relying on JavaScript, which is both convenient and efficient.
1. Use built-in properties for basic verification
HTML5 introduces some properties of form elements that can be directly used to control input rules. Common ones include required , min , max , pattern , type , etc.
-
required: means that the field cannot be empty. -
type="email"ortype="url": The browser will automatically verify that the input meets the email or URL format. -
minandmax: Used to limit numerical values or date ranges. -
pattern: Used in conjunction with regular expressions, it can define more complex input formats.
For example, a must-complete mailbox input box can be written like this:
<input type="email" required>
When a user submits, if the input does not conform to the email format, the browser will automatically pop up a prompt.
2. Use CSS pseudo-class to enhance user feedback
In addition to functional verification, visual feedback is also important. HTML5 provides :valid and :invalid pseudo-classes, which can be used to add styles to the input box with CSS.
For example, you can set the border of invalid input to red:
input:invalid {
border-color: red;
}In this way, the user can see the error immediately during the input process, without having to wait until after submitting to know where the error occurred. However, it should be noted that some browsers will add a red border or other style when the input is illegal by default, and may require manual reset to maintain consistency.
3. Use JavaScript to make more flexible controls
Although the built-in verification of HTML5 is already very practical, in some complex scenarios, JavaScript is still needed to achieve more flexible control. For example, you want to check the password strength in real time when the user enters it, or make some extra judgments before submitting.
You can use checkValidity() method to trigger verification manually:
const form = document.querySelector('form');
form.addEventListener('submit', function(event) {
if (!form.checkValidity()) {
event.preventDefault();
// Custom prompts can be added here}
}); You can also combine setCustomValidity() method to set custom error messages, which are suitable for more complex business logic.
4. Optimization and compatibility considerations of prompt information
The default browser prompt message is usually stiff, and the styles of different browsers are not uniform. If you want to unify the prompt style, you can consider hiding the default prompt and using JavaScript with a custom prompt box to achieve it.
In addition, although HTML5 form verification is well supported in modern browsers, if you need to support old browsers (such as IE9 and below), you still need to cooperate with JavaScript for downgrade processing.
In general, HTML5 form validation provides a simple and practical solution, and the rational use of built-in properties and JavaScript can greatly improve the usability of forms without adding too much work. Of course, front-end verification cannot replace back-end verification, and the final data verification still needs to be completed on the server side.
The above is the detailed content of Implementing HTML5 Form Validation Techniques. For more information, please follow other related articles on the PHP Chinese website!
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