"For" loops within classes JS w3School do not work?

[JKowalski]

Hello, to my experience the following does not work (tryit-editor w3School), but it does with a "while" loop instead. Are "for" loops not allowed within classes?

<p id="demo">result</p>

class Test{

  counter(){
    var result=0;
    for(i=0;i<10;i++){
      result++;
    }
    return result;
  }

  counter2(){
    var result=0;
    while(result<10){
      result++;
    }
    return result;
  }

}

var obj=new Test();
document.getElementById("demo").innerHTML=obj.counter();
//document.getElementById("demo").innerHTML=obj.counter2();

[Ingolme]

It has an error because you forgot to declare i with the var keyword.

[Sherin]

You have not declare I with datatype of  int ,var then you facing error in for loop