Form verification can be implemented through HTML5 built-in properties, including required, min, max, pattern and type, to ensure that the user enters the correct data; for example, use <input type="email" required> to verify the mailbox format. The setCustomValidity() method of JavaScript can be customized, such as listening to input events and setting prompt information. At the same time, you can add style feedback for valid or invalid inputs by CSS pseudo-classes:valid and:invalid, such as red and green borders to distinguish between errors and correct inputs.
Form verification is an important step in web development to ensure that users enter correct and effective data. HTML5 provides some native form verification functions, which allows us to complete basic verification work without writing a line of JavaScript. Rational use of these features not only improves the user experience, but also reduces the pressure on the backend to process wrong inputs.
Use built-in form properties
HTML5 adds many form-related attributes, such as required , min , max , pattern , etc. They can be used directly on the <input> tag to help us realize basic data format control.
-
required: mark a field as required -
minandmax: limit the value or date range -
pattern: Use regular expressions to match input -
type: The browser's verification logic can be automatically triggered by setting different input types (such as email, url, number).
For example, if you want the user to enter a legal email address, you can write it like this:
<input type="email" required>
The browser will automatically check whether the email format is in line with the user's submission and give a prompt.
Custom error message
While HTML5's default prompts are already practical, sometimes you may want to display more friendly or more product-style prompts. At this time, JavaScript can be used to interfere with the default behavior and customize the prompt content.
You can use setCustomValidity() method to set an error message. For example:
const input = document.querySelector('input');
input.addEventListener('input', function () {
if (input.validity.valueMissing) {
input.setCustomValidity('Please enter your name, it's very important~');
} else {
input.setCustomValidity('');
}
});This method is particularly suitable for situations where complex judgments are required based on business rules. However, remember to clear the custom error message every time you complete verification, otherwise the form submission may be stuck.
Enhance feedback with pseudo-class styles
In addition to functional verification, visual feedback is also important. Users should be able to see at a glance which fields are in trouble. HTML5 provides some pseudo-classes, such as :valid and :invalid , which can add styles based on whether the input meets the requirements.
You can write CSS like this:
input:invalid {
border-color: red;
}
input:valid {
border-color: green;
}In this way, when the user input does not meet the conditions, the border will turn red, making it easier for the user to notice the problem. Of course, for better accessibility, it is recommended to use it with icons and text prompts.
Basically that's it. The HTML5 form verification mechanism is already quite powerful. As long as you make rational use of built-in properties and some simple scripts, you can achieve both concise and effective front-end verification logic.
The above is the detailed content of HTML5 Forms Validation Techniques. For more information, please follow other related articles on the PHP Chinese website!
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