JS- this

Question 1

What is this in JavaScript?

Answer 1

an implicit parameter, reference to the object that is executing the current function

Question 2

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

Answer 2

not explicitly defined but understood

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

there is no this, because the greet method is not being called so NOTHING, NONEXISTENT

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!” the greet method of the character object is being called

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” because the hello variable is a property of the window object

Question 7

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

Answer 7

you can’t know in a definition, only exists in a call

Question 8

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

Answer 8

the object to the left of the dot