Delete

Execute this code:

var name = 'John',
 obj = {
 name: 'James'
 },
 Animal,
 mammal;
Animal = function(){};
Animal.prototype.name = 'animal';
mammal = new Animal();
mammal.name = 'mammal';
delete name;
console.log('#1: ' + name);
delete obj.name;
console.log('#2: ' + obj.name);
delete obj.toString;
console.log('#3: ' + obj.toString);
delete mammal.name;
console.log('#4: ' + mammal.name);

The execution of this code logs:

#1: John

#2: undefined

#3: function toString() { [native code] }

#4: animal

John is logged because name is a global variable and global variables can't be deleted.

__match_answer_and_solution__

undefined is logged because we have deleted the name property of obj, properties or members of objects can be deleted excluding the properties or members of the global object.

__match_answer_and_solution__

function toString() { [native code] } is logged because toString is an inherited method from Object and inherited methods or members can't be deleted.

__match_answer_and_solution__

animal is logged because we have deleted the own mammal.name property but the inherited property is shown.

__match_answer_and_solution__