js this basics

Question 1

What is this in JavaScript?

Answer 1

object that represents the lexical scope of the reference at call time

Question 2

What does it mean to say that this is an “implicit parameter”?

Answer 2

it is a parameter that exists even though it is not explicitly defined

Question 3

When is the value of this determined in a function; call time or definition time?

Answer 3

call time

Question 4

What does this refer to in the following code snippet?
var character = {
  firstName: 'Mario',
  greet: function () {
    var message = 'It\'s-a-me, ' + this.firstName + '!';
    console.log(message);
  }
};

Answer 4

the object character

Question 5

Given the above character object, what is the result of the following code snippet? Why?
character.greet();

Answer 5

‘It’s-a-me Mario!’

this.character inside the method returns character the object

Question 6

Given the above character object, what is the result of the following code snippet? Why?
var hello = character.greet;
hello();

Answer 6

‘It’s-a-me undefined’

this.firstName is undefined

Question 7

How can you tell what the value of this will be for a particular function or method definition?

Answer 7

you cannot unless you know when and where this is

Question 8

How can you tell what the value of this is for a particular function or method call?

Answer 8

check the lexical scope?