","welcome Message":"All current users can sign in using their existing email & password.If your User Name had any Spaces or Special Characters like $\" Underscore.
Our validation script will ensure that the user enters their name before the form is sent to the server. Try pressing the Send Details button without filling anything in the "Your Name" field.You might like to open the source code for this form in a separate window, so that you can refer to it throughout the tutorial.For example, if your form has a box for the user to type their email address, you might want your form handler to check that they've filled in their address before you deal with the rest of the form.There are two main methods for validating forms: (usually done using Java Script).We want to the user to agree to our imaginary Terms and Conditions before they send the form, so we'll check to make sure they've clicked the checkbox: in any one of the above cases, if one or more of our checks fail, the form will not be sent to the server.
If the user has not completed more than one field, then they will see an alert box appear for each field that is missing.
In all cases, the form is called That's checking the value's equality with a null String (two single quotes with nothing between them).
When you are asking a reader for their email address, you can use a simple » address validation function to make sure the address has a valid structure. Each option in a drop-down box is indexed in the array Annoyingly, there is no simple way to check which radio button out of a group is selected — you have to check through each element, linked with Boolean AND operators .
When you submit a form to a CGI program that resides on the server, it is usually programmed to do its own check for errors.
If it finds any it sends the page back to the reader who then has to re-enter some data, before submitting again.
You can see that the page consists of a Java Script function called That's all there is to simple Java Script form validation!