How to check in js that user has checked the checkbox in Google recaptcha?

Google has a call back option for when the checkbox is checked.

Add this to your form element:

data-callback="XXX"

Example:

<div class="g-recaptcha" data-callback="recaptchaCallback" data-sitekey="== xxxxxx =="></div>

And a disable attribute to your submit button.

Example:

<button id="submitBtn" disabled>Submit</button>

Then a create a callback function and write whatever code you need.

Example:

function recaptchaCallback() {
    $('#submitBtn').removeAttr('disabled');
};

You can also call the grecaptcha object to check. grecaptcha.getResponse(); is empty when unchecked and has the verification code when checked.

grecaptcha.getResponse().length === 0 when unchecked

function isCaptchaChecked() {
  return grecaptcha && grecaptcha.getResponse().length !== 0;
}

if (isCaptchaChecked()) {
  // ...
}

To check if google recaptcha is checked or not you can do it by the following code :

<script>

if(grecaptcha && grecaptcha.getResponse().length > 0)
{
     //the recaptcha is checked
     // Do what you want here
     alert('Well, recaptcha is checked !');
}
else
{
    //The recaptcha is not cheched
    //You can display an error message here
    alert('Oops, you have to check the recaptcha !');
}

</script>

To check if google recaptcha v2 is checked or not you can do it by the following code :

var checkCaptch = false;
     var verifyCallback = function(response) {
        if (response == "") {
             checkCaptch = false;
         }
         else {
             checkCaptch = true;
         }
     };
     $(document).ready(function() {
         $("#btnSubmit").click(function() {
             if (checkCaptch && grecaptcha.getResponse()!="") {
                  //Write your success code here
             }
         });
     })