Please explain this Javascript closure exercise

In order to understand this you must know what is the
difference between a function call and a reference to a function. As well as how scopes
work in javascript.

Assuming you do know these things,
let's get explaining.

So you first have a variable
hidden that is being assigned a value of
mystery(3). So immediately look at the function
mystery and see what it returns. it returns a
reference to an inner function
mystery2. So now hidden holds a
reference, meaning that it has no actual numeric value.
Following you have a second variable declaration
var jumble =
mystery3(hidden);. Now in order to know what
jumble holds you need to look at the function
mystery3 and the value it returns. It, again, returns a
reference to an inner function mystery4. So now the two
variables you have contain references to inner functions of the closures
mystery and
mystery3.

Now let's have a look at
var result = jumble(2). Executing
jumble(2) is an actual function call to the function that
jumble holds a reference to, which is
mystery4. When mystery4 runs you see
it requires a parameter bonus, which will be
2 given from the line var result =
jumble(2). It returns param(6) + bonus.
bonus is 2, ok, but what is
param(6)? That is the value given to
jumble: hidden, which was a reference
to mystery2, remember? So running
param(6) will execute mystery2 with a
parameter 6

And so, tracing back
the functions may have turned out a little confusing, but let's follow that with actual
values to make it a little clearer ( if that's even a word
).

Executing var result =
jumble(2) will give us a return value of param(6) +
2 to get param(6) we go into
mystery2 with multiplier = 6, where we
set multiplier = 6 * input. Our input is equal to
3+2=5, so multiplier becomes
6*5=30 and as a return value we multiply that by
4 which is our var secret. By the end
of the execution of mystery2 we have a value of
120, which is returned to our param(6)
in mystery4. And if you remember that our
bonus was 2,
120+2=122 Voila!

I get the feeling
I didn't do a very good job at explaining this simply, but that's probably the best I
could do. Hope that helped!