Stop form refreshing page on submit

How would I go about preventing the page from refreshing when pressing the send button without any data in the fields?

The validation is setup working fine, all fields go red but then the page is immediately refreshed. My knowledge of JS is relatively basic.

In particular I think the processForm() function at the bottom is ‘bad’.

HTML

<form id="prospects_form" method="post">
    <input id="form_name" tabindex="1" class="boxsize" type="text" name="name" placeholder="Full name*" maxlength="80" value="" />
    <input id="form_email" tabindex="2" class="boxsize" type="text" name="email" placeholder="Email*" maxlength="100" value="" />
    <input id="form_subject" class="boxsize" type="text" name="subject" placeholder="Subject*" maxlength="50" value="FORM: Row for OUBC" />
    <textarea id="form_message" class="boxsize" name="message" placeholder="Message*" tabindex="3" rows="6" cols="5" maxlength="500"></textarea>
        
    <button id="form_send" tabindex="5" class="btn" type="submit" onclick="return processForm()">Send</button>
    <div id="form_validation">
        <span class="form_captcha_code"></span>
        <input id="form_captcha" class="boxsize" type="text" name="form_captcha" placeholder="Enter code" tabindex="4" value="" />
    </div>
    <div class="clearfix"></div>
</form>

JS

$(document).ready(function() { 

// Add active class to inputs
$("#prospects_form .boxsize").focus(function() { $(this).addClass("hasText"); });
$("#form_validation .boxsize").focus(function() { $(this).parent().addClass("hasText"); });
// Remove active class from inputs (if empty)
$("#prospects_form .boxsize").blur(function() { if ( this.value === "") { $(this).removeClass("hasText"); } });
$("#form_validation .boxsize").blur(function() { if ( this.value === "") { $(this).parent().removeClass("hasText"); } });


 
///////////////////
// START VALIDATION
$("#prospects_form").ready(function() {
    
    // DEFINE GLOBAL VARIABLES
    var valName = $('#form_name'),
        valEmail = $("#form_email"),
        valEmailFormat = /^(([^<>()[]\.,;:s@"]+(.[^<>()[]\.,;:s@"]+)*)|(".+"))@(([[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}])|(([a-zA-Z-0-9]+.)+[a-zA-Z]{2,}))$/,
        valMsg = $('#form_message'),
        valCaptcha = $('#form_captcha'),
        valCaptchaCode = $('.form_captcha_code');
        


    // Generate captcha
    function randomgen() {
        var rannumber = "";
        // Iterate through 1 to 9, 4 times
        for(ranNum=1; ranNum<=4; ranNum++){ rannumber+=Math.floor(Math.random()*10).toString(); }
        // Apply captcha to element
        valCaptchaCode.html(rannumber);
    }
    randomgen();
    
    
    // CAPTCHA VALIDATION
    valCaptcha.blur(function() {
        function formCaptcha() {
            if ( valCaptcha.val() == valCaptchaCode.html() ) {
                // Incorrect
                valCaptcha.parent().addClass("invalid");
                return false;
            } else {
                // Correct
                valCaptcha.parent().removeClass("invalid");
                return true;
            }
        }
        formCaptcha();
    });
    
    // Remove invalid class from captcha if typing
    valCaptcha.keypress(function() {
        valCaptcha.parent().removeClass("invalid");
    });
    
    
    // EMAIL VALIDATION (BLUR)
    valEmail.blur(function() {
        function formEmail() {
            if (!valEmailFormat.test(valEmail.val()) && valEmail.val() !== "" ) {
                // Incorrect
                valEmail.addClass("invalid");
            } else {
                // Correct
                valEmail.removeClass("invalid");
            }
        }
        formEmail();
    });
    
    // Remove invalid class from email if typing
    valEmail.keypress(function() {
        valEmail.removeClass("invalid");
    });
    
    
    // VALIDATION ON SUBMIT
    $('#prospects_form').submit(function() {
        console.log('user hit send button');

        // EMAIL VALIDATION (SUBMIT)
        function formEmailSubmit() {
            if (!valEmailFormat.test(valEmail.val())) {
                // Incorrect
                valEmail.addClass("invalid");
            } else {
                // Correct
                valEmail.removeClass("invalid");
            }
        }
        formEmailSubmit();

        // Validate captcha
        function formCaptchaSubmit() {
            if( valCaptcha.val() === valCaptchaCode.html() ) {
                // Captcha is correct
            } else {
                // Captcha is incorrect
                valCaptcha.parent().addClass("invalid");
                randomgen();
            }
        }
        formCaptchaSubmit();
        
        
        // If NAME field is empty
        function formNameSubmit() {
            if ( valName.val() === "" ) {
                // Name is empty
                valName.addClass("invalid");
            } else {
                valName.removeClass("invalid");
            }
        }
        formNameSubmit();
        
        
        // If MESSAGE field is empty
        function formMessageSubmit() {
            if ( valMsg.val() === "" ) {
                // Name is empty
                valMsg.addClass("invalid");
            } else {
                valMsg.removeClass("invalid");
            }
        }
        formMessageSubmit();
    
    
        // Submit form (if all good)
        function processForm() {
            if ( formEmailSubmit() && formCaptchaSubmit() && formNameSubmit() && formMessageSubmit() ) {
                $("#prospects_form").attr("action", "/clients/oubc/row-for-oubc-send.php");
                $("#form_send").attr("type", "submit");
                return true;
            } else if( !formEmailSubmit() ) {
                valEmail.addClass("invalid");
                return false;
            } else if ( !formCaptchaSubmit() ) {
                valCaptcha.parent().addClass("invalid");
                return false;
            } else if ( !formNameSubmit() ) {
                valName.addClass("invalid");
                    return false;
                } else if ( !formMessageSubmit() ) {
                    valMsg.addClass("invalid");
                    return false;
                } else {
                    return false;
                }
            }
        });
    });
    // END VALIDATION
    /////////////////
});

Answer

You can prevent the form from submitting with

$("#prospects_form").submit(function(e) {
    e.preventDefault();
});

Of course, in the function, you can check for empty fields, and if anything doesn’t look right, e.preventDefault() will stop the submit.

Without jQuery:

var form = document.getElementById("myForm");
function handleForm(event) { event.preventDefault(); } 
form.addEventListener('submit', handleForm);