The output of the above code for first 'this.a' is '10' and second 'this.a' inside function x is ‘undefined’. Reason being that ‘this’ keyword when directly used inside an object’s method points to the object itself but in the above code ‘this’ keyword is present inside x() function of the vir() method , so its not being directly used in object’s method vir() , so it would refer to window object and there is no variable ‘a’ in the window object so output will be ‘undefined’. 

let obj ={
a: 10,
vir : function(){
  x();
  console.log(this.a); //output 10
  function x(){
  console.log(this.a) // undefined
  }
 }
}
obj.vir();