Can someone please explain why this JavaScript output behaves this way?

Question

var x = 0
x = (++x)-1
console.log(x)
//output is 0

var x = 0;
var array = [2,9,7,4];
array[x] = (++x)-1;

console.log(array[x]);

//output is 9

I’m having trouble understanding why the second scenario x is treated as a 1 and not a zero. I would have expected output for console.log(array[x]) to be 2. Please help.

Answer 1

X equals 1 because in the line
array[x] = (++x) - 1;
x is incremented, so it becomes 1. Don't let the -1 afterwards fool you, it doesn't affect the original value of x since it only works with a copy of that value.

Answer 2

like Shadow said it's because the answer (equation) is always executed before the variable