HTML5 form polyfiller
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Yep here is another bicycle for HTML 5 forms validation. jQuery.f5 was was written for the following reasons:

  • Brain-free usage.
  • Avoiding treatment of builtin features.
  • Low-level HTML5 form support: validity Object, validationMessage property, form and field checkValidity and field setCustomValidity methods.
  • HTML5 input types support: email, url, number.
  • HTML5 input attributes: placeholder, required, pattern.
  • HTML5 field invalid and input events.

Only one dependency - jQuery.

f5 tested on Chrome, MSIE 7+ and FF 3.6+.


Add jQuery and jQuery.f5 scripts to your site and fire 'f5'.

You can find basic example in tests/test-f5-base.html.

By default, f5 tries to behave as close as possible to standart HTML5 forms. All differences due to the lack of some features in the old browsers.

Low-level functions and events

f5 provides standart HTML5 form low-level functions and properties.

validity object always represents field validity state. See this for details.

validationMessage property always represents error message. See this for details.

validity and validationMessage updated with every change of the field.

checkValidity method returns validity.valid property of field, if value of this property is false, invokes invalid event. Form also has checkValidity method. On invocation, it invokes checkValidity of each field and returns false if at least one field is invalid. You can find details here.

For MSIE f5's checkValidity method also fires valid events if field is valid.

With setCustomValidity method you can set a custom error message on a field and it will be in an invalid state until the custom message is set back to an empty string. Details here.

Validation chain

All restrictions of field in HTML5 are arrayed in a chain: required, field type, pattern, min and max for numbers.

For example, if you need a field with non-blank email, you must provide required.

<input type='email' required> 


Without any options f5 tries to behave as close as possible to standart HTML5 forms. In following example f5 is initialized with default options:

    classes : {
        valid : 'valid',
        invalid : 'invalid',
        required : 'required'
    messages : {
        required : "Please fill out this field.",
        pattern : "Please match the requested format.",
        email : "Please enter an email address.",
        url : "Please enter URL",
        number : "Please enter numeric value"
    error: {
        force: false,      
        create: function(){
            var err = $('<span class="error"></span>');
            return err;

Let's dig them one by one.


With classes option you can define own classes to form states. Of course this matters only for old browsers.

    classes : {
        valid : 'good',
        invalid : 'bad'

Old browsers not support :valid, :invalid and :required CSS pseudo-selectors. In order to deal with them f5 uses CSS classes with the same names. So you need to define this rules in CSS:

input[type=text].valid, input[type=text]:valid
input[type=email].invalid, input[type=email]:invalid
input[type=email].invalid.required, input[type=email]:invalid:required

Avoid to use :not pseudo-selector. IE handles it incorrectly.

Another bug in IE is ignoring . rule in set with ::

input:valid, input.valid    <- not works in IE
input.valid    <- works in IE

Error messages

Old browsers don't know anything about error messages. By default f5 provides simply english messages. You can override them with messages option:

    messages : {
        required : "Not blank please!"

For old browsers f5 uses following mechanism to show error messages by default: after each input f5 adds span#error element whose value is the last error message.

<input type='email' class='invalid'>
 ^                         ^ added to represent state for old browsers
 | with "something" value for example                              
<span class='error focus'>Please enter an email address.</span>
 ^                  ^ last error message
 | this element added upon initialisation 

In CSS you can define rules to display message depending state of field via CSS sibling selectors (+ or ~):

.error {
    color: #600;
    display: none;

input.invalid:focus + .error, textarea.invalid:focus + .error,
input:invalid:focus + .error, textarea:invalid:focus + .error  {
    display: block;

Webkit has bug with adjacent/general sibling selectors and pseudo classes. You can fix this by following bugfix:

body { -webkit-animation: bugfix infinite 1s; }
@-webkit-keyframes bugfix { from { padding: 0; } to { padding: 0; } }

To override default error messages you need provide error.create option:

    error: {
        create: function(){
            var err = $('Any stuff<span class="error"></span>');
            return err;

By default f5 not sets error messages for modern browsers. To force f5's error messages you need set error.force option to true.

    error: {
        force: true

You can find example in tests/test-f5-force.html.

jquery.f51: Dark side of power

Ok, f5 was conceived with the dark intentions. So, f51 is all about usability:

  • Intellectual submit button. It never enabled if form contains invalid fields.
  • Brain-free async validation.
  • Override Submit function.

You can find example of f51 in tests/test-f51.html.

f51 takes all options of f5. By default f51 forces error messages.

Async validation

To validate field in asyncronous manner you need to do two things. First - add validator function to f51 options:

    validators: {
        someValidator: function(callback){
            var that = this;
            // Long-long...
                (this.value == 'somevalue') ? 
                    callback() : callback('Value must be "somevalue".');
            } ,3000);

... And second - bind this validator to field:

<input type='text' validate='someValidator' required 
    placeholder='Non-blank "somevalue".'>

Validator function takes one argument - callback function and executes in field context. Callback function takes one argument - message. field is considered correct if message is blank or undefined.

Validator function will be invoked only if all builtin validations of field is passed and field hasn't custom error.

Pending state

For time of async validation f51 adds '.pending' class to field and sets "Checking..." custom error. You can define CSS rules for this:

/* For input */
input.pending {
    border-color: #DDC !important;
input.pending:focus {
    background-color: #FFFFF9;

/* ... and message */
input.pending:focus ~ .error, textarea.pending:focus ~ .error {
    color: #777;
    display: block;

Also you can override class and message by setting following options:

    // ...
    classes: { 
        pending: 'pending' 
    messages: { 
        pending: 'Checking...' 


f51 tries to avoid unnecessary async validations. Async validation starts a bit later last change of field. You can change interval by setting poll option:

    // ...
    poll: 500 // 0.5 second

Submit override

Instead of banal sending form to server, you can do something own:

    submit: function() {
        return false;

This will provide a more predictable behavior than jQuery.submit because f51 cleans and checks form before.