Objects function 'this'

Question 1

When a function is invoked a new ________ context is created.

Answer 1

execution

Question 2

Every time a _____ is run, ‘this’ variable is created.

Answer 2

function

Question 3

Argument

Answer 3

The parameters you pass to a function

Question 4

Does JavaScript pass variables by reference or by value?

Answer 4

Yes, primitive types are passed by value.

Question 5

Primitive types are passed by ______. and Objects are passed by ______.

Answer 5

reference

Question 6

What does passed-by value mean?

Answer 6

If you change the value of a primitive type inside a function, the changes won’t affect the variable in the outer scope. Because you passed a copy set in different locations.

Question 7

What does passed-by reference mean?

Answer 7

You’re passing something that points to something else vs the copy. Any changes made to that reference will also be changed in the outer scope.

Question 8

== is called?

Answer 8

double equal

Question 9

=== is called?

Answer 9

strict equal

Question 10

strict equal checks for?

Answer 10

both type as well as value equality

Question 11

double equal checks for?

Answer 11

only checks for the equality of the values.

Question 12

Why does the js engine produce “true” for 0==’0’?

Answer 12

A double equality only checks for the value so the engine tries to convert the number on the left side of the equal sign to a string.

Question 13

How do you check if a type is a number?

Answer 13

isNaN();

Question 14

NaN == NaN produces and why?

Answer 14

false. type coercion. It’s coercing NaN into a string to check if its a number.

Question 15

undefined == null produces what result.

Answer 15

True. undefined is null and null is undefined

Question 16

console.log(typeof(null)); produces what result?

Answer 16

“object”. JavaScript incorrectly reports the type of null as object.

Question 17

console.log(NaN == “1”);

Answer 17

NaN equal to ANYTHING is always false, even when compared to itself. (one of those weird moments in JS)

Question 18

the “this” keyword is determined by the ______ context.

Answer 18

calling. It’s determined by the way in which a function is called.

Question 19

“this” is strict mode is always

Answer 19

undefined

Question 20

A method is a function attached to an ______.

Answer 20

object

Question 21

this is lexically bound, which means its value is derived from the ____________.

Answer 21

context where they are defined.

Question 22

Can you bind an existing object method to remap its ‘this’ value?

Answer 22

Yes

Question 23

const car = {
  maker: 'Ford',
  model: 'Fiesta',
  drive() {
    console.log(`Driving a ${this.maker} ${this.model} car!`)
  }
}
const anotherCar = {
  maker: 'Audi',
  model: 'A4'
}

What does this result in?

Answer 23

Driving a Audi A4 car!

Question 24

const car = {
  maker: 'Ford',
  model: 'Fiesta'
}
const drive = function() {
  console.log(`Driving a ${this.maker} ${this.model} car!`)
}.bind(car)

Answer 24

Driving a Ford Fiesta car!

Question 25

The first parameter you pass to call() or apply() is always bound to _____.

Answer 25

‘this’.

Question 26

The difference between call() and apply() is …

Answer 26

just that the apply() wants an array as the arguments list, while call() accepts a variable number of parameters, which passes as function arguments.

Question 27

const car = {
  maker: 'Ford',
  model: 'Fiesta'
}
const drive = function(kmh) {
  console.log(`Driving a ${this.maker} ${this.model} car at ${kmh} km/h!`)
}
drive.call(car, 100)

Results in?

Answer 27

Driving a Ford Fiesta car at 100 km/h!