javascript-this

Question 1

What is this in JavaScript?

Answer 1

the object that is currently executing the code.

Question 2

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

Answer 2

it is included as a paremeter even though it was not passed. It is implicit.

Question 3

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

Answer 3

at 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

character object

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!

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!

Question 7

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

Answer 7

if there is no value to the left of the dot when the function is called, then by default, this will be the global window object.

Question 8

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

Answer 8

if there is no value to the left of the dot when the function is called, then by default, this will be the global window object.