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>