Question

What is the best JQuery way to ensure that all input fields with the attribute “required” are completed

Answer 1

Use the .filter() method to check the value of each and then check the length property of the result:

var incomplete = $("input[required]").filter(function () {
    return this.value === "";
});
if (incomplete.length) {
    alert("Please fill in all the required fields");
}

Note that an attribute named required will invalidate your HTML. data-required would be valid HTML5, however, or you could just give them all a class and use that as the selector (which would also be more efficient).

You could also use one of the validation plugins out there: http://google.com/search?q=jquery+validation.