How do I use javascript to prevent form submission because of empty fields?

Question

How do I make a script in javascript to output an error and prevent form submission with empty fields in the form? Say the form name is \"form\" and the input name is \"name\".

Answer 1

Claudio's answer is great. Here's a plain js option for you. Just says to do nothing if field is empty - and to submit if not.

If you need to validate more than one, just add an && operator in the if statement and add the same syntax for OtherFieldName

function checkForm(form1)
{
    if (form1.elements['FieldName'].value == "")
    {
        alert("You didn't fill out FieldName - please do so before submitting");
        return false;
    }
    else
    {
        form1.submit();
        return false;
    }
}