For Adding Recaptcha

gistfile1.txt

// add js
<script src='https://www.google.com/recaptcha/api.js'></script>

// in html
<div class="g-recaptcha" data-sitekey="YOUR_SITEKEY"></div>

// for showing visual feedback if captcha is not selected
<script>

(function(){

  var formsToValidate = ['#YOUR_FORM_ID'];

  formsToValidate.forEach(function(item){

    $(item).submit(function(event) {
      var recaptcha  = $(this).find('textarea[name=g-recaptcha-response]').val();
      if (recaptcha === "") {
        event.preventDefault();
        $(this).find('.g-recaptcha > div').css('border', '1px solid red');
      } else {
        $(this).find('.g-recaptcha > div').css('border', 'none');
      }
    });

  });

}());

</script>