Javascript quiz - question #3 analysis

gistfile1.txt

/*
Question: #3 (http://perfectionkills.com/javascript-quiz/)
 
(function(x){
    delete x;
    return x;
  })(1);
 
A.  1  [correct]
B.  null
C.  undefined
D.  Error
*/
 
// Analysis
 
// "The delete operator removes a property from an object."
// "delete is only effective on an object's properties. It has no effect on variable or function names."
// -- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/delete
 
(function(x){
    delete x;
    console.log(x);  // 1
    return x;
})(1);
 
var y = 5; // declares a new variable, y
console.log(delete y); // false
console.log(y);  // 5
 
z = 101;  // creates the property z on the global object (i.e. window)
console.log(delete z); // true
console.log(z); // undefined