Question 1

What is the output of foo.apply(obj, [5, 3]) where foo returns this.x + y + z and obj.x is 10?

Accepted Answer

18. apply sets this to obj (this.x = 10) and passes [5, 3] as y and z. 10 + 5 + 3 = 18.

Question 2

Can you re-bind a function that is already bound in JavaScript?

Accepted Answer

No. The first bind wins. bound.bind(newObj) does not change this. The bound function keeps the original this from the first bind call.

Question 3

How do you convert arguments to an array using call?

Accepted Answer

Array.prototype.slice.call(arguments). This borrows the slice method from Array.prototype and applies it to the array-like arguments object.

Question 4

What happens if you call bind on an arrow function?

Accepted Answer

Nothing. The arrow function's this is lexical (inherited from the enclosing scope). bind, call, and apply cannot change an arrow's this.

What is the output of foo.apply(obj, [5, 3]) where foo returns this.x + y + z and obj.x is 10?

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