When the form is submitted - either by hitting Enter or clicking on the Submit button - the (the 'value' of the field called 'input' belonging to the form). In a real-life situation you will most likely have more fields to check, and more complicated conditions, but the principle remains the same.Other form values are available using a similar syntax, although this becomes more complicated if you're using SELECT lists, checkboxes or radio buttons (see below for examples). All you need to do is extend the command is encountered, execution of the function is halted.Validating form input with Java Script is easy to do and can save a lot of unnecessary calls to the server as all processing is handled by the web browser.It can prevent people from leaving fields blank, from entering too little or too much or from using invalid characters.I've coded a working form, all checks are great but for some reason the hardest part is trying to stop form submission before validation.So i have places to insert the stop validation code, but just cant find any that works.Otherwise a browser with Java Script disabled, or a hacker trying to compromise your site, can easily submit invalid data. The first test in the example is therefore only necessary in order to provide a different error message when the input is blank.The purpose of a form validation script is to return a boolean value ('s to reference form fields, but that can lead to namespace conflicts and why make things more complicated than necessary.
Only when all conditions have been satisfied do we reach the command, in which case the form will be submitted.Radio buttons are implemented as if they were an array of checkboxes.To find out which value (if any) has been selected, you need to loop through the array until you find which one has been selected: In the case of a single radio button we have nothing to loop through so just return either it's value, if the radio button is checked, or false.The idea is to create a set of “validation descriptors” associated with each element in a form.The “validation descriptor” is nothing but a string specifying the type of validation to be performed.