HTML5必需属性不适用于AJAX提交

Question

I am trying to do some basic validation for a simple newsletter form I have that only requires an email. The way I have this form/input within the page, there really isn't room to add any jQuery validate error messages, so I was trying to add a simple HTML 5 required attribute, but the form submits regardless if blank.

What would be the best way to add some simple validation to this so the form checks for an email address, it is filled in, and min length of 4 characters?

<form action="" method="POST" id="newsletter-form">
    <input type="email" id="footer-grid1-newsletter-input" placeholder="Your Email Address" required>
    <input type="submit" id="footer-grid1-newsletter-submit" name="submit" value='&nbsp'>
</form>

$("#footer-grid1-newsletter-submit").on("click", function (event) {
    event.preventDefault();
    var newsletter_email = $("#footer-grid1-newsletter-input").val();
    var targeted_popup_class = jQuery(this).attr('data-popup-open');
    $.ajax({ 
        url: "newsletterSend.php", 
        type: "POST",
        data: {
            "newsletter_email": newsletter_email
        },
        success: function (data) {
            //  console.log(data); // data object will return the response when status code is 200
            if (data == "Error!") {
                alert("Unable to insert email!");
                alert(data);
            } else {
                $("#newsletter-form")[0].reset();
                $('.newsletter-popup').fadeIn(350).delay(2000).fadeOut();
            }
        },
        error: function (xhr, textStatus, errorThrown) {
            alert(textStatus + " | " + errorThrown);
            //console.log("error"); //otherwise error if status code is other than 200.
        }
    });
});

Answer 1

The reason is because the validation is done on the submit event of the form, yet you have hooked your event to the click of the submit button. Try this:

$("#newsletter-form").on("submit", function (event) {
    event.preventDefault();
    // your code...
});

Working example

With regard to validating a minimum input length, you can use the pattern attribute:

<input type="email" id="footer-grid1-newsletter-input" placeholder="Your Email Address" pattern=".{3,}" required>