Why this mark (!) not working?

Question

https://code.sololearn.com/WAG4IFDbx8s0/?ref=app

Answer 1

"!" is a unary not operator, which means it can take only one exression towards right of it.. and what ever Boolean result it gets it converts it to its opposite value
But you have used it within two expressions , therefore it is not working

Answer 2

You used logical not operator you should use logical or || instead of !
x=5;
y=++x;
x=y++;
eval("x=y+7");
document.write("<br>"+x+"</br>");
document.write("<br>"+y+"</br>");
x+=y*=7;
document.write(x,y);
var hy=7;
var num=(hy==7||x==y)? "perfect" : "miserable";
document.write(num);

Answer 3

What purpose are trying to use it for?
|| => Or
&& => And