<form class="validate">
	<div>
		<label for="text">Name</label>
		<input type="text" id="text" required>
	</div>

	<div>
		<label for="email">Email</label>
		<input type="email" id="email" title="The domain portion of the email address is invalid (the portion after the @)." pattern="^([^\x00-\x20\x22\x28\x29\x2c\x2e\x3a-\x3c\x3e\x40\x5b-\x5d\x7f-\xff]+|\x22([^\x0d\x22\x5c\x80-\xff]|\x5c[\x00-\x7f])*\x22)(\x2e([^\x00-\x20\x22\x28\x29\x2c\x2e\x3a-\x3c\x3e\x40\x5b-\x5d\x7f-\xff]+|\x22([^\x0d\x22\x5c\x80-\xff]|\x5c[\x00-\x7f])*\x22))*\x40([^\x00-\x20\x22\x28\x29\x2c\x2e\x3a-\x3c\x3e\x40\x5b-\x5d\x7f-\xff]+|\x5b([^\x0d\x5b-\x5d\x80-\xff]|\x5c[\x00-\x7f])*\x5d)(\x2e([^\x00-\x20\x22\x28\x29\x2c\x2e\x3a-\x3c\x3e\x40\x5b-\x5d\x7f-\xff]+|\x5b([^\x0d\x5b-\x5d\x80-\xff]|\x5c[\x00-\x7f])*\x5d))*(\.\w{2,})+$" required>
	</div>

	<div>
		<label for="url">URL</label>
		<input type="url" id="url" title="The URL is a missing a TLD (for example, .com)." pattern="^(?:(?:https?|HTTPS?|ftp|FTP):\/\/)(?:\S+(?::\S*)?@)?(?:(?!(?:10|127)(?:\.\d{1,3}){3})(?!(?:169\.254|192\.168)(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[a-zA-Z\u00a1-\uffff0-9]-*)*[a-zA-Z\u00a1-\uffff0-9]+)(?:\.(?:[a-zA-Z\u00a1-\uffff0-9]-*)*[a-zA-Z\u00a1-\uffff0-9]+)*(?:\.(?:[a-zA-Z\u00a1-\uffff]{2,}))\.?)(?::\d{2,5})?(?:[/?#]\S*)?$" required>
	</div>

	<div>
		<strong>Radio Buttons</strong>
		<label class="label-normal">
		    <input type="radio" name="radio" id="radio-1" required>
		    Yes
		</label>
		<label class="label-normal">
		    <input type="radio" name="radio" id="radio-2" required>
		    No
		</label>
	</div>

	<input type="submit" class="button" value="Submit">
</form>

body {
	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen", "Ubuntu", "Cantarell", "Fira Sans", "Droid Sans", "Helvetica Neue", sans-serif;
	font-size: 112.5%;
	margin-left: auto;
	margin-right: auto;
	max-width: 40em;
	width: 88%;
}  

/**
 * Form Styles
 */
label {
	display: block;
	font-weight: bold;
	margin-bottom: 0.5em;
}

.label-normal {
	font-weight: normal;
}

.description-date {
	color: #808080;
	font-size: 0.8em;
	font-weight: normal;
}

.supports-date .description-date {
    display: none;
}

input,
select {
	display: inline-block;
	font-size: 1em;
	margin-bottom: 1em;
	padding: 0.25em 0.5em;
	width: 100%;
}

[type="checkbox"],
[type="radio"] {
	margin-bottom: 0.5em;
	width: auto;
}

.button {
	background-color: #0088cc;
	border: 1px solid #0088cc;
	border-radius: 1px;
	color: #ffffff;
	display: inline-block;
	font-size: 0.9375em;
	font-weight: normal;
	line-height: 1.2;
	margin-right: 0.3125em;
	margin-bottom: 0.3125em;
	padding: 0.5em 0.6875em;
	width: auto;
}

.button:active,
.button:focus,
.button:hover {
	background-color: #005580;
	border-color: #005580;
	color: #ffffff;
	text-decoration: none;
}

.button:active {
	box-shadow: inset 0 0.15625em 0.25em rgba(0, 0, 0, 0.15), 0 1px 0.15625em rgba(0, 0, 0, 0.05);
}

/**
 * Errors
 */
.error {
	border-color: red;
}

.error-message {
	color: red;
	font-style: italic;
	margin-bottom: 1em;
}

// Add the novalidate attribute when the JS loads
var forms = document.querySelectorAll('.validate');
for (var i = 0; i < forms.length; i++) {
    forms[i].setAttribute('novalidate', true);
}


// Validate the field
var hasError = function (field) {

    // Don't validate submits, buttons, file and reset inputs, and disabled fields
    if (field.disabled || field.type === 'file' || field.type === 'reset' || field.type === 'submit' || field.type === 'button') return;

    // Get validity
    var validity = field.validity;

    // If valid, return null
    if (validity.valid) return;

    // If field is required and empty
    if (validity.valueMissing) return 'Please fill out this field.';

    // If not the right type
    if (validity.typeMismatch) {

        // Email
        if (field.type === 'email') return 'Please enter an email address.';

        // URL
        if (field.type === 'url') return 'Please enter a URL.';

    }

    // If too short
    if (validity.tooShort) return 'Please lengthen this text to ' + field.getAttribute('minLength') + ' characters or more. You are currently using ' + field.value.length + ' characters.';

    // If too long
    if (validity.tooLong) return 'Please shorten this text to no more than ' + field.getAttribute('maxLength') + ' characters. You are currently using ' + field.value.length + ' characters.';

    // If number input isn't a number
    if (validity.badInput) return 'Please enter a number.';

    // If a number value doesn't match the step interval
    if (validity.stepMismatch) return 'Please select a valid value.';

    // If a number field is over the max
    if (validity.rangeOverflow) return 'Please select a value that is no more than ' + field.getAttribute('max') + '.';

    // If a number field is below the min
    if (validity.rangeUnderflow) return 'Please select a value that is no less than ' + field.getAttribute('min') + '.';
  
      // If pattern doesn't match
    if (validity.patternMismatch) {

        // If pattern info is included, return custom error
        if (field.hasAttribute('title')) return field.getAttribute('title');

        // Otherwise, generic error
        return 'Please match the requested format.';

    }

    // If all else fails, return a generic catchall error
    return 'The value you entered for this field is invalid.';

};


// Show an error message
var showError = function (field, error) {

    // Add error class to field
    field.classList.add('error');
  
    // If the field is a radio button and part of a group, error all and get the last item in the group
    if (field.type === 'radio' && field.name) {
        var group = document.getElementsByName(field.name);
        if (group.length > 0) {
            for (var i = 0; i < group.length; i++) {
                // Only check fields in current form
                if (group[i].form !== field.form) continue;
                group[i].classList.add('error');
            }
            field = group[group.length - 1];
        }
    }

    // Get field id or name
    var id = field.id || field.name;
    if (!id) return;

    // Check if error message field already exists
    // If not, create one
    var message = field.form.querySelector('.error-message#error-for-' + id );
    if (!message) {
        message = document.createElement('div');
        message.className = 'error-message';
        message.id = 'error-for-' + id;
        
        // If the field is a radio button or checkbox, insert error after the label
        var label;
        if (field.type === 'radio' || field.type ==='checkbox') {
            label = field.form.querySelector('label[for="' + id + '"]') || field.parentNode;
            if (label) {
                label.parentNode.insertBefore( message, label.nextSibling );
            }
        }

        // Otherwise, insert it after the field
        if (!label) {
            field.parentNode.insertBefore( message, field.nextSibling );
        }

    }
    
    // Add ARIA role to the field
    field.setAttribute('aria-describedby', 'error-for-' + id);

    // Update error message
    message.innerHTML = error;

    // Show error message
    message.style.display = 'block';
    message.style.visibility = 'visible';

};


// Remove the error message
var removeError = function (field) {

    // Remove error class to field
    field.classList.remove('error');
    
    // Remove ARIA role from the field
    field.removeAttribute('aria-describedby');

    // If the field is a radio button and part of a group, remove error from all and get the last item in the group
    if (field.type === 'radio' && field.name) {
        var group = document.getElementsByName(field.name);
        if (group.length > 0) {
            for (var i = 0; i < group.length; i++) {
                // Only check fields in current form
                if (group[i].form !== field.form) continue;
                group[i].classList.remove('error');
            }
            field = group[group.length - 1];
        }
    }

    // Get field id or name
    var id = field.id || field.name;
    if (!id) return;
    

    // Check if an error message is in the DOM
    var message = field.form.querySelector('.error-message#error-for-' + id + '');
    if (!message) return;

    // If so, hide it
    message.innerHTML = '';
    message.style.display = 'none';
    message.style.visibility = 'hidden';

};


// Listen to all blur events
document.addEventListener('blur', function (event) {

    // Only run if the field is in a form to be validated
    if (!event.target.form.classList.contains('validate')) return;

    // Validate the field
    var error = hasError(event.target);
  
    // If there's an error, show it
    if (error) {
        showError(event.target, error);
        return;
    }

    // Otherwise, remove any existing error message
    removeError(event.target);

}, true);


// Check all fields on submit
document.addEventListener('submit', function (event) {

    // Only run on forms flagged for validation
    if (!event.target.classList.contains('validate')) return;

    // Get all of the form elements
    var fields = event.target.elements;

    // Validate each field
    // Store the first field with an error to a variable so we can bring it into focus later
    var error, hasErrors;
    for (var i = 0; i < fields.length; i++) {
        error = hasError(fields[i]);
        if (error) {
            showError(fields[i], error);
            if (!hasErrors) {
                hasErrors = fields[i];
            }
        }
    }

    // If there are errrors, don't submit form and focus on first element with error
    if (hasErrors) {
        event.preventDefault();
        hasErrors.focus();
    }

    // Otherwise, let the form submit normally
    // You could also bolt in an Ajax form submit process here

}, false);