Looking at the excerpt, there are definitely things I would do differently like using data attributes to map the front-end form fields to marketo fields and making use of loops to make mapping field values dynamic.
Annotated example code below
As a side note, you've got some IDs appearing twice, once in your front-end form and once in your marketo form, #zipCode and #partnerName.
<form id="contactForm">
<label>First Name</label><br/>
<input type="text" name="FN" id="FirstName" data-mktoName="FirstName" placeholder="First Name"><br/><br/>
<label>Last Name</label><br/>
<input type="text" name="LN" id="LastName" data-mktoName="LastName" placeholder="Last Name"><br/><br/>
<label>Email</label><br/>
<input type="email" name="EM" id="Email" data-mktoName="Email" placeholder="Email Address"><br/><br/>
<label>Company</label><br/>
<input type="text" name="CO" id="Company" data-mktoName="Company" placeholder="Company"><br/><br/>
<input type="checkbox" name="optional1" id="optional1" data-mktoName="optional1"> <label for="optional1">Optional 1</label><br/>
<input type="checkbox" name="optional2" id="optional2" data-mktoName="optional2"> <label for="agree1">Optional 2</label><br/>
<input type="checkbox" name="agree1" id="agree1" data-mktoName="agree1"> <label for="agree2">Agree 1</label><br/><br/>
<input id="submit-btn" type="submit" value="Submit" class="btn btn-blue my-2">
</form>
<script>
function getMktoFormData($form){
var mktoFields = $('[data-mktoName]:input'),
mktoCheckboxFields = mktoFields.filter('[type="checkbox"]'),
formDataObject= {};
$.each(mktoFields,function(i){
formDataObject[$(this).attr('data-mktoName')] = $(this).val();
});
$.each(mktoCheckboxFields,function(i){
if($(this).prop("checked")){
formDataObject[$(this).attr('data-mktoName')] = 'yes';
} else {
formDataObject[$(this).attr('data-mktoName')] = 0;
}
});
return formDataObject;
}
var $form = $("#contactForm"),
articleUrl = $form.find('#articleUrl').val(),
mktoBaseUrl = "https://cname.domain.com",
mktoMunchkinId = "123-ABC-456",
mktoFormId = 1234;
$('body').append("<form id='mktoForm_"+mktoFormId+"' style='display:none;visibility:hidden;opacity:0;'></form>");
MktoForms2.loadForm(mktoBaseUrl,mktoMunchkinId,mktoFormId,function(form){
form.onSuccess(function(values, followUpUrl) {
location.href = '/accounts/thanks?gatedArticle='+articleUrl;
return false;
});
});
$('#contactForm').submit(
function(e){
e.preventDefault();
var payload = getMktoFormData($form),
alerts = [],
re = /^(([^<>()\[\]\\.,;:\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,}))$/;
if(!re.test(String(payload.Email).toLowerCase())){
console.log('email invalid');
alerts.push(alerts.length+1 + ") The email address you entered is invalid");
}
if (!payload.checkbox) {
console.log('checkbox not checked');
alerts.push(alerts.length+1 + ") You must check the checkbox");
}
if (alerts.length) {
alert("Please note:\n" + alerts.join("\n") );
} else {
console.log('submit');
$form.find(':input').prop('readonly','readonly');
$('#submit-btn').hide();
$form.append('<p><img src="loading.gif"/> Just a moment</p>');
var mktoForm = MktoForms2.getForm(mktoFormId);
mktoForm.addHiddenFields(payload);
mktoForm.submit();
}
}
);
</script>
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