Do you really know JS?

Hi!, this is my first post and I wanted to make it a little and simple javascript quiz but I wont give you the answers, the idea is that you put your answers in the comments and discussed which ones are correct and which are not, so let's begin!

1.- What is the result of this expression? (or multiple ones)

                 ["1", "2", "3"].map(parseInt)

a) ["1","2", "3"]
b) [1,2,3]
c) [1, NaN, NaN]
d) other (give your answer)

2.- What is the result of this expression? (or multiple ones)

                 [typeof null, null instanceof Object]

a) ["object", true]
b) ["object", false]
c) ["object", null]
d) other (give your answer)

3.- What is the result of this expression? (or multiple ones)

                  var x = [].reverse;
                  x();

a) window
b) other
c) undefined
d) true

4.- What is the result of this expression? (or multiple ones)

                   2 == [[[2]]]

a) false
b) true
c) error
d) undefined

5.- What is the result of this expression? (or multiple ones)

                   var a = /123/,
                   b = /123/;
                   a == b
                   a === b

a) true, true
b) true, false
c) false, true
d) other

6.- What is the result of this expression? (or multiple ones)

          var a = {}, b = Object.prototype;
          [a.prototype === b, Object.getPrototypeOf(a) === b]

a) [true, false]
b) [true, true]
c) [false, false]
d) none of the above

Comments

[Dragoș Străinu]

I think 4 out of 6 is a good score!

Bonus task:
Make a function that satisfies these conditions!

fn(1)(2)(3)(4) == 10 // true
fn(1)(2) == 3 // true
fn(1)(0)(0)(0)(0)(3) == 4 // true
fn(1) == 1 // true

[clementDeb]

hello, thanks for the question, could you explain why the 5 is false, false ? please

[José Muñoz]

because you're comparing references, not their values.

SO Thread: stackoverflow.com/questions/110327...

[clementDeb]

because they are regex which means object. cheers

[William Silva]

Why error with these expressions?

[inventivemejo]

I'm new to this website, and not able to select options or locate ans.
Would somebody help me to find answers?

[Gerardo]

You can't select the options, my idea was that you paste your answers here in the comment section and discuss them with the community haha

[pavandkvrk]

Q1 : B
I think Q2 : A