Can type of defined variable be undefined in javascript?

Here is an example code from Google about how to safely initialize its recaptcha service https://developers.google.com/recaptcha/docs/loading

<script async src="https://www.google.com/recaptcha/api.js"></script>

<script>    
  if(typeof grecaptcha === 'undefined') {
    grecaptcha = {};
  }

  grecaptcha.ready = function(cb){
    //How is it possible for grecaptcha to be undefined here?
    if(typeof grecaptcha === 'undefined') {
      
      const c = '___grecaptcha_cfg';
      window[c] = window[c] || {};
      (window[c]['fns'] = window[c]['fns']||[]).push(cb);
    } else {
      cb();
    }
  }

  grecaptcha.ready(function(){
    grecaptcha.render("container", {
      sitekey: "ABC-123"
    });
  });
</script>

As you can see grecaptcha.ready is a function and it again checks if(typeof grecaptcha === 'undefined'). But how can grecaptcha be undefined at the time when grecaptcha.ready is called? As I understand grecaptcha has already been initialized as a property of global object and it’s value is {} hence it’s type should be "object"

Answer

It’d have to be code elsewhere, but sure, it’s a global object, so a malicious actor could potentially overwrite it, e.g. you could have something like:

var grecaptcha = { 
     start() {
         var that = this;
         return new Promise((resolve, reject) => {
             setTimeout(() => {
                 if (that.ready) {
                     that.ready(that)
                 }
                 resolve(true);
             }, 5000);
             let remaining = 4;
             let interval = setInterval(() => {
                 console.log(remaining--);
                 if (remaining == 0) {
                     clearInterval(interval);
                 }
             }, 1000);
         });
     }
 
};

grecaptcha.start().then(() => console.log('But we still do stuff with it'));

if(typeof grecaptcha === 'undefined') {
    grecaptcha = {};
}

grecaptcha.ready = function(cb){
    console.log(typeof grecaptcha);
}

setTimeout(() => grecaptcha = undefined, 1000)