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 .
That brings our total file size up to 15.5kb unminified—still 9× smaller than the Mail Chimp validation script.
Usually you'll just want to check if Modern Web Design Using Java Script & DOMJava Script is back!
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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.