This JavaScript article tutorial guides you how to create HTML form element validators that work more efficient. Throughout this JavaScript article tutorial, you are able to be better at using JavaScript to process, parse form input data such as password, valid email address, URL address, number/string values, etc.

Please go to the inner post-page for full details and instructions, and read more other JavaScript article tutorial from same author:
- JavaScript Date and Time Validating Tutorials

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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.

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.

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;
}

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:

input:required:invalid, input:focus:invalid {
  background-image: 
url('data:image/png;base64,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');

  background-position: right top;
  background-repeat: no-repeat;
  -moz-box-shadow: none;
}
input:required:valid {
  background-image: 
url('data:image/png;base64,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');

  background-position: right top;
  background-repeat: no-repeat;
}

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 input field appears in Safari with either the image or the 'sprite' backgrounds (there is no difference between the two options):

The same styling can be extended to textarea elements, but won't work for checkboxes, select elements, etc. For the latter you might want to place the valid/invalid markers alongside the element or format those input elements using borders, background colours, etc.

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:

// 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; }
    }
  }
}

7. INPUT patterns for different data types

URL input pattern:

input type="url" pattern="https?://.+"

IP Address input pattern:

input type="text" pattern="\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}"

Date input pattern:

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+"

Feel free to send any patterns you find useful using the Feedback form.

8. References

• A Form of Madness - Dive Into HTML5
• A List Apart: Articles: Forward Thinking Form Validation
• A List Apart: Articles: Inline Validation in Web Forms
• Have a Field Day with HTML5 Forms
• HTML5 input types | 456 Berea Street
• W3C: Forms - HTML5

Related Articles

• JavaScript: Form Validation
• JavaScript Form Validating Tips, Code and Examples
• JavaScript Date and Time Validating Tutorials
• JavaScript: Form Validation: Credit Cards and Dates
• Design Better HTML5 Form Element Validator

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