Start Validating radio button javascript

Validating radio button javascript

You can then adapt this form to your own requirements.

To check for the possibility of the user leaving the entire group unchecked, an additional if statement only needs to test the variable "found_it" for a value of null. Remember - comparison operators compare two operands for equality. The not operator evaluates a null value in the same way it evaluates a false value, so it can be used to test found_it to see if it has been assigned a value.

The if/else can be constructed in two different ways using two different operators. To keep from becoming confused by the not operator, just think of it as a shorthand way of saying, "found_it==false".

A Java Script check is useful because it stops the form from being submitted if there is a problem, saving lots of time for your readers.

The CGI script is still more reliable, as it always works regardless of whether Java Script is enabled on the client-side or not; but having this extra safety barrier is a nice thing to have in place.

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.

We're going to be checking the form using a function, which will be activated by the form's Validating this form would be considerably simpler than one containing radio buttons or select boxes, but any form element can be accessed.

Below are the ways to get the value from all types of form elements.

There are two main methods for validating forms: (usually done using Java Script).

Server-side validation is more secure but often more tricky to code, whereas client-side (Java Script) validation is easier to do and quicker too (the browser doesn't have to connect to the server to validate the form, so the user finds out instantly if they've missed out that required field! In this tutorial we'll build a simple form with client-side Java Script validation.

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.