HTML: HTML5 Form Validation Examples
HTML5 introduced several built-in form validation attributes that can be added to form elements to perform client-side validation without using JavaScript. Here are some commonly used validation attributes:
Required: Specifies that an input field must be filled out before submitting the form.
html<input type="text" required>Pattern: Allows you to specify a regular expression that the input value must match.
html<input type="text" pattern="[A-Za-z]{3}">Min and Max: Sets the minimum and maximum values for numeric input fields.
html<input type="number" min="1" max="100">Email: Validates that the input is a valid email address.
html<input type="email">URL: Validates that the input is a valid URL.
html<input type="url">Minlength and Maxlength: Specifies the minimum and maximum number of characters allowed in a text field.
html<input type="text" minlength="5" maxlength="10">Pattern Error Message: Providing a custom error message for pattern validation.
html<input type="text" pattern="[A-Za-z]{3}" title="Three letters only">Custom Error Message: Using the
requiredattribute with a custom error message.html<input type="text" required="required" oninvalid="this.setCustomValidity('Custom error message')" oninput="setCustomValidity('')">
These attributes can be used in conjunction with <input>, <textarea>, <select>, and <button> elements to ensure input data meets specified criteria before submitting the form.
1. The 'required' attribute
The simplest change you can make to your forms is to mark a text input field as 'required':Your Name: <input type="text" name="name" required>This informs the (HTML5-aware) web browser that the field is to be considered mandatory.
We have actually created our own valid/invalid formatting using CSS to override the browser default, but more on that later. That's why you may see something like the following in the example above:
Before you type anything into the box a red marker is shown. As soon as a single character has been entered this changes to a green marker to indicate that the input is 'valid'.
Using CSS you can place markers inside or alongside the input box, or simply use background colours and borders as some browsers do by default.
The required attribute can also be applied to checkboxes when you want them to be mandatory.
2. Different INPUT types
This is where HTML5 really gets interesting and more useful. Along with the text input type, there are now a host of other options, including email, url, number, tel, date and many others.INPUT type="email"
Email Address: <input type="email" name="email" required placeholder="Enter a valid email address">Note that for this example we've made use of another HTML5 attribute placeholder which lets us display a prompt or instructions inside the field - something that previously had to be implemented using messy onfocus and onblur JavaScript events.
The above code displays an input box as follows:
Again, different browsers implement this differently. In Opera it's sufficient to enter just *@* for the input to be accepted. In Safari, Chrome and Firefox you need to enter at least *@-.-. Obviously neither example is very limiting, but it will prevent people from entering completely wrong values, such as phone number, strings with multiple '@'s or spaces.
Here is how it appears in Safari (with our CSS formatting to show the (in)valid state):
INPUT type="url"
Website: <input type="url" name="website" required>Again, the input box appears as normal:
As mentioned above, we can improve on this by making use of the pattern attribute which accepts a JavaScript regular expression. So the code above becomes:
Website: <input type="url" name="website" required pattern="https?://.+">Now our input box will only accept text starting with http:// or https:// and at least one additional character:
INPUT type="number" and type="range"
The number and range input types also accept parameters for min, max and step. In most cases you can leave out step as it defaults to 1.Here you see an example including both a number input, typically displayed as a 'roller' and a range input displayed as a 'slider':
Age: <input type="number" size="6" name="age" min="18" max="99" value="21"><br>
Satisfaction: <input type="range" size="2" name="satisfaction" min="1" max="5" value="3">As with other HTML5 input types, browsers that don't recognise the new options will default to simple text inputs. For that reason it's a good idea to include a size for the input box.
The slider option is a bit bizarre in that no values are displayed, but may be useful for more 'analog' inputs. There are some bugs with the number input in that if you don't set a max value, clicking 'down' with the input blank will result in a very large number.
Here is how the two inputs are displayed in Safari:
They are currently not supported in Firefox 4 Beta.
If you want to restrict the input of a text field to numbers without having the up/down arrows associated with the input box, you can always just set the input type to text and use a pattern of "\d+" (one or more numbers).
INPUT type="password"
We have a separate article with details on validating passwords using HTML5, including JavaScript code for customising the browser generated alert messages.3. Other HTML5 INPUT types
Other HTML5 input types include:- color
- date
- datetime
- datetime-local
- month
- search
- tel
- time
- week
The tel input type is handy for the iPhone as it selects a different input keyboard. There is no pattern-matching set by default so you would have to implement that yourself using the pattern attribute to accept only certain characters.
The color input is meant to let you select a hex-code from a colour wheel - or similar - but as yet doesn't appear to have been implemented in the wild.
The other date- and time-related options do have an effect at least in Opera, with pop-up calendars and other devices appearing to assist with input. While it would be great to see something like this in every browser, for now you probably need to stick with the ubiquitous JavaScript plugins.
4. Styling valid/invalid inputs using CSS
While the code we're using is slightly more complicated, this should get you started:
input:required:invalid, input:focus:invalid {
/* insert your own styles for invalid form input */
-moz-box-shadow: none;
}The first set of styles can be used to mark an input box as 'invalid', by adding an icon, colouring the text or borders or similar. It will apply to inputs that are required but empty, or to inputs that have a required format/pattern which hasn't yet been met.
The -moz-box-shadow style is there just to prevent Firefox 4 Beta from adding it's default red border.
For inputs that are both required and 'valid' you can use the following:
input:required:valid {
/* insert your own styles for valid form input */
}Some of the articles below, particularly the first two, provide other style/scripting options and solutions for supporting older browsers.
In tandem with the new input types and attributes provided by HTML5, CSS3 gives us some new pseudo-classes we can use to provide visual clues to the user as to which form fields are required, which are optional, and which contain validation errors.
Required fields can use the
:required pseudo-class:input:required {
background:hsl(180, 50%, 90%);
border:1px solid #999;
}:optional pseudo-class:input:optional {
background:hsl(300, 50%, 90%);
border:1px dotted hsl(180, 50%, 90%);
}:valid, :invalid, :in-range, and :out-of-range pseudo-classes:input:valid,
input:in-range {
background:hsl(120, 50%, 90%);
border-color:hsl(120, 50%, 50%);
}
input:invalid,
input:out-of-range {
border-color:hsl(0, 50%, 50%);
background:hsl(0, 50%, 90%);
}5. Sample styling using images and sprites
As shown above, once you've added HTML5 attributes to your form elements, they can be easily styled using CSS so that each input field is clearly marked as valid or invalid.<style type="text/css">
input:required:invalid, input:focus:invalid {
background-image: url(/images/invalid.png);
background-position: right top;
background-repeat: no-repeat;
}
input:required:valid {
background-image: url(/images/valid.png);
background-position: right top;
background-repeat: no-repeat;
}
</style>Here you can see the above styles applied to a required input field:
This solution is still more complicated than it needs to be as it requires two extra images to be loaded. Fortunately, we can assume that all browsers supporting HTML5 form validation techniques will also support images being replaced in the CSS by 'Base64 encoded datasets'.
Using a service such as Spritebaker or other techniques, the above style settings become:
<style type="text/css">
input:required:invalid, input:focus:invalid {
background-image: url(data:image/png;base64 background-position: right top;
background-repeat: no-repeat;
-moz-box-shadow: none;
}
input:required:valid {
background-image: url(data:image/png;base64,=);
background-position: right top;
background-repeat: no-repeat;
}
</style>The above code can now be copied directly to your CSS style sheet. There's no need to copy any images and, especially if your style-sheets are gzip-compressed, there will be next to no impact on load times. In a few minutes you could have your whole website updated.
For the browser-impaired, this is how the required input field will appear in Safari with either the image or the Data URI backgrounds:
6. Fallback for the placeholder attribute
The following JavaScript, placed or included at the end of the page, should enable support for the placeholder attribute in INPUT fields at least for Internet Explorer 8+, Firefox and Opera:<script type="text/javascript">
// ref: http://diveintohtml5.org/detect.html
function supports_input_placeholder()
{
var i = document.createElement('input');
return 'placeholder' in i;
}
if(!supports_input_placeholder()) {
var fields = document.getElementsByTagName('INPUT');
for(var i=0; i < fields.length; i++) {
if(fields[i].hasAttribute('placeholder')) {
fields[i].defaultValue = fields[i].getAttribute('placeholder');
fields[i].onfocus = function() { if(this.value == this.defaultValue) this.value = ''; }
fields[i].onblur = function() { if(this.value == '') this.value = this.defaultValue; }
}
}
}
</script>7. INPUT patterns for different data types
URL input pattern:
input type="url" pattern="https?://.+"IPv4 Address input pattern:
input type="text" pattern="\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}"Date input pattern (dd/mm/yyyy or mm/dd/yyyy):
input type="text" pattern="\d{1,2}/\d{1,2}/\d{4}"Price input pattern:
input type="text" pattern="\d+(\.\d{2})?"Latitude/Longitude input pattern:
input type="text" pattern="-?\d{1,3}\.\d+"---------------------------------------------------->>>>>><input type="url">
<input type="email">
<input type="password">
<input name="q" placeholder="Go to a Website">
<input type="number" min="0" max="10" step="2" value="6"><input type="date">:
<input type="datetime">:
<input type="month">:
<input type="week">:
<input type="time">:
<input type="search"><input type="color">,
<input id="q" required>
<input id="q" autofocus>---------------------------------------------------->>>>>>HTML5 Simple and powerful responsive web templates
http://www.html5webtemplates.co.uk/templates.html
Source http://www.the-art-of-web.com/html/html5-form-validation/
http://html5pattern.com/Names
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