Submitting modal form via Ajax
It looks like your firing this on the submit event, which is why its....submitting? Maybe this would work better?
$(function() {$('#tag-form-submit').on('click', function(e) { e.preventDefault(); $.ajax({ type: "POST", url: "{{ path('addTag') }}", data: $('form.tagForm').serialize(), success: function(response) { alert(response['response']); }, error: function() { alert('Error'); } }); return false;});});