Can someone debug this for me?

Question

var x = 0;
for(; x <= 8; x++){
x += x - x++;
console.log(x);
}
console.log("final value: ", x);

//i found this in a javascript challenge

Answer 1

I ran it on my pc, in vs code. It works fine. But I think the third line isn't doing much. When I comment it out, the result is the same.

Answer 2

I think, it will be evaluated like
x = x + ( x - x--) ; // the post increment here x-- is pushed into stack for evaluation separately.. then x = x + 1 is updated. But previous calculatuon
x+( x- x--) is evaluated and result is stored in x so overrites x++ value with x +(x-x) which is just equalto x = x + ( x - x) ;
So in loop, x value unchages..

Final value : 9
Hope it helps..

Answer 3

Jayakrishna🇮🇳
thank you but I am not able to get it completely

Answer 4

Paul that's interesting

Answer 5

0 += 1-1
1 += 2-2
2 +=3-3
Basicaly you are doing x += 0

Answer 6

Raul Ramirez
how is it 1-1, 2-2, 3-3 and so on...?

Answer 7

Cpu calculates right to left

Answer 8

Because post increment, the value uses first in expression then increment
So x - x++ is done like x - x, x++

x += x - x++ is done like
x = ( x + ( x - x ) ), x++
x++ update x but it is overritten by value ( x + ( x - x)) which is actually equal to (x - 0) => x
Instead of storing back in x , use any other variable, you can see x++ value .

I thought, your doubt is in
x += x - x-- result.
Where you not understood my reply.. Tell about specific lines..
But hope it clears now..

Answer 9

Thanks Jayakrishna🇮🇳 !
I got it now.

Answer 10

Harsha S no but it does have an order of operations similar to it

Answer 11

You're welcome..

Answer 12

I use vscode to debug things, i hope this helps 🙂

Answer 13

No error when i ran it

Answer 14

Raul Ramirez yeah, right. i forgot that.
but does it not follow BODMAS too?

Answer 15

Dada Praise Oluwatomiwa
so, how did you learn to copy paste?