Start Validating html form

Validating html form

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.

More and more browsers now support the constraint validation API, and it's becoming reliable.

This API consists of a set of methods and properties available on each form element.

For these examples we have created our own valid/invalid CSS formatting to override the browser default. That's why you may see something like the following: 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'.

Form validation helps us to ensure that users fill out forms in the correct format, making sure that submitted data will work successfully with our applications.

This article will tell you what you need to know about form validation.

Again, not very helpful, but it will stop people trying to input their email address or other such nonsense. Careful examination of the RFCs associated with email addresses has been conducted repeatedly and has been proven to require the use of recursion in order properly determine the validity of an email address using the full set of RFC specifications.

As mentioned above, we can improve on this by making use of the are already implicit so the input has to match the entire expression. If anyone wants to contribute a more thorough expression to test for valid email or url format, feel free to post it using the Feedback option above.. Since it is not possible to recurse when using a regular expression it is also not possible to create a truly accurate regex for doing email address validation.

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. On the i Phone/i Pad the different input types are associated with different keyboards, making it easier for people to complete your online forms.

In other web browsers they can be used in combination with the .

Sure there have been all kinds of whacky plug-ins over the years aimed at achieving this, but never a single standard that we could work towards.