how to delete a element in object javascript code example

Example 1: javascript delete key from object

let person = {
  firstname: 'John',
  lastname: 'Doe'
}

console.log(person.firstname);
// expected output: "John"

delete person.firstname;

console.log(person.firstname);
// expected output: undefined

Example 2: javascript remove property from object

var person = {"first_name": "Billy","last_name": "Johnson"};
delete person.last_name; //delete last_name property

Example 3: javascript remove function from object

var obj = {
  func: function(a, b) {
    return a + b;
  }
};
delete obj.func;
obj.func(); // Uncaught TypeError: obj.func is not a function