ReCaptcha v2 client side events

Another solution is to set data-callback directly on the g-recaptcha div, like this

<script type="text/javascript">
  var imNotARobot = function() {
    console.info("Button was clicked");
  };
</script>

<div class="g-recaptcha" data-callback="imNotARobot" data-sitekey="key"></div>

You can configure reCAPTCHA to give a callback on successful validation using the data-callback attribute on the g-recaptcha tag or via the 'callback' parameter if using explicit rendering.

See https://developers.google.com/recaptcha/docs/display#render_param

Example using explicit rendering:

var myCallback = function(val) { console.log(val); };
grecaptcha.render(
   document.getElementsById('my-recaptcha-placeholder'), 
   {
     callback: myCallback, 
     sitekey: mySiteKey
   });