Increment rule inconsistencies

Question

Problem 1

What is the output of this code?

var x = 9;
var y = x++;
alert (++x * y);

Sololearn says the answer is 99. I got 90 because I was under the impression that in the 2nd line, y = 9 and x = 9 since x++ is a post fix increment. So by the 3rd line (++x made 10 for me since the value didn't change from the 2nd line).

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Problem 2

What will be alerted?

n = 2;
m = (n++ * 12);
alert(m);

Sololearn says the answer is 24.

The increment rules are inconsistent with the answers to both these questions. How come in the first question we add the +1 to get 10 in the second line then add +1 again to get 11, but in the next question we don't add the +1, even though in both questions they're both post fix increments ?

I hope I'm not confusing anyone. But I'll try to explain clearer if it's too confusing.

Answer 1

var x = 9;
var y = x++;
alert (++x * y);

Line 1: assign 9 to x.

Line 2: postfix increment assigns the value of x to y, then increment x
:- y=9 and x = 10.

Line 3: Here there is another operation on x which is prefix increment which brings the value of x to 11 and then multipled to y which is 9 from line 2.
:- ans = 11 * 9 = 99.

Answer 2

V F happy to help

Answer 3

y=x++ means y will be 9. x is raised after the deed to 10.

++x means, that x is raised again, this time before the deed.

So it's 11*9.

So in line 2, x is still 9. In line 3 it has been changed to 10, but before the calculation, it is changed once more.

n++*12 means that n is raised after the calculation.

So m is 24 now, and after that, n becomes 3.

Answer 4

Zone , n is incremented after its value is used in the statement, system will see your statement as
n=2;
m=n*12; //Value of n used is 2
n=n+1; //Now "n" is incremented
Alert(m); //2*12 =24
This is how a post increment operator works, value of n is incremented after tha statement gets finished if you would have used pre increment the it would have incremented and then used in the statement.

Answer 5

Arsenic I'm aware that n is Incremented to 3 in the second problem. But if that's the case, why isn't the answer 36 instead of 24?

Answer 6

Meny Evolving clear explanation! Thanks!

Answer 7

Zone I think you are not clear with the concept of post increment operator.
In your first problem:-
In second line first value of x(which is 9) is assigned to y and then x is incremented to 10.
In second problem:-
Again in second line, in the whole statement value of n used will be 2 and then at the end of the statement n is incremented to 3

Hope you got it if not then tell me, I will try to make it more clear

Answer 8

Arsenic HonFu thanks I think I'm getting the hang of it now

Answer 9

How to change characteristic value of a variable in python

Answer 10

Meny Evolving So in line 2, if postfix increment, the value will assign first and then increment?

Var x = 9;
Then var y =x++;
Or var 9 = 10;
Then alert (++x * y);
Or alert (11 * 9);

So postfix increment