The value of a text input box (or a textarea or password input) is available using the syntax that tells you which option has been selected.The illustration below shows this relationship: Note that the 'I' in selected Index needs to be capitalised - Java Script functions and variables are always case-sensitive. Read more about the humble checkbox in our HTML5 Checkbox Validation article.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: defines a locally scoped variable.HTML5 brought us several No longer, do we need crazy long regex patterns to validate form fields.Using the html attributes we have available as well as some hard-working, built-in Java Script functions, we can do simple client-side form validation.
” Server-side checking entails the user submitting the form to the server, such as ASP, C# or PHP, then the server code checks and returns an error if it finds one. Client-side validation usually means: Java Script intercepting the form before it’s submitted to check for errors, possibly using regex.
Validating form input with Java Script is easy to do and can save a lot of unnecessary calls to the server.
It can prevent people from leaving fields blank, from entering too little or too much or from using invalid characters.
Using client side Java Script is an efficient way to validate the user input in web forms.
When there are many fields in the form, the Java Script validation becomes too complex.
You'll see that the all validation scripts presented on this and subsequent pages adhere to the same basic format.